We are currently solving the following issue within our repository. Here is the issue text:
--- BEGIN ISSUE ---
CSS bundles generation breaks background images relative urls
This is a bug related to PR #1300.


--- END ISSUE ---

Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
--- BEGIN FILES ---
Path: `Products/CMFPlone/resources/browser/combine.py`
Content:
```
1 from zExceptions import NotFound
2 from Acquisition import aq_base
3 from datetime import datetime
4 from plone.registry.interfaces import IRegistry
5 from plone.resource.file import FilesystemFile
6 from plone.resource.interfaces import IResourceDirectory
7 from Products.CMFPlone.interfaces import IBundleRegistry
8 from Products.CMFPlone.interfaces.resources import (
9     OVERRIDE_RESOURCE_DIRECTORY_NAME,
10 )
11 from StringIO import StringIO
12 from zope.component import getUtility
13 from zope.component import queryUtility
14 
15 PRODUCTION_RESOURCE_DIRECTORY = "production"
16 
17 
18 def get_production_resource_directory():
19     persistent_directory = queryUtility(IResourceDirectory, name="persistent")
20     if persistent_directory is None:
21         return ''
22     container = persistent_directory[OVERRIDE_RESOURCE_DIRECTORY_NAME]
23     try:
24         production_folder = container[PRODUCTION_RESOURCE_DIRECTORY]
25     except NotFound:
26         return "%s/++unique++1" % PRODUCTION_RESOURCE_DIRECTORY
27     timestamp = production_folder.readFile('timestamp.txt')
28     return "%s/++unique++%s" % (
29         PRODUCTION_RESOURCE_DIRECTORY, timestamp)
30 
31 
32 def get_resource(context, path):
33     if path.startswith('++plone++'):
34         # ++plone++ resources can be customized, we return their override
35         # value if any
36         overrides = get_override_directory(context)
37         filepath = path[9:]
38         if overrides.isFile(filepath):
39             return overrides.readFile(filepath)
40 
41     resource = context.unrestrictedTraverse(path)
42     if isinstance(resource, FilesystemFile):
43         (directory, sep, filename) = path.rpartition('/')
44         return context.unrestrictedTraverse(directory).readFile(filename)
45     else:
46         if hasattr(aq_base(resource), 'GET'):
47             # for FileResource
48             return resource.GET()
49         else:
50             # any BrowserView
51             return resource()
52 
53 
54 def write_js(context, folder, meta_bundle):
55     registry = getUtility(IRegistry)
56     resources = []
57 
58     # default resources
59     if meta_bundle == 'default' and registry.records.get(
60         'plone.resources/jquery.js'
61     ):
62         resources.append(get_resource(context,
63             registry.records['plone.resources/jquery.js'].value))
64         resources.append(get_resource(context,
65             registry.records['plone.resources.requirejs'].value))
66         resources.append(get_resource(context,
67             registry.records['plone.resources.configjs'].value))
68 
69     # bundles
70     bundles = registry.collectionOfInterface(
71         IBundleRegistry, prefix="plone.bundles", check=False)
72     for bundle in bundles.values():
73         if bundle.merge_with == meta_bundle and bundle.jscompilation:
74             resources.append(get_resource(context, bundle.jscompilation))
75 
76     fi = StringIO()
77     for script in resources:
78         fi.write(script + '\n')
79     folder.writeFile(meta_bundle + ".js", fi)
80 
81 
82 def write_css(context, folder, meta_bundle):
83     registry = getUtility(IRegistry)
84     resources = []
85 
86     bundles = registry.collectionOfInterface(
87         IBundleRegistry, prefix="plone.bundles", check=False)
88     for bundle in bundles.values():
89         if bundle.merge_with == meta_bundle and bundle.csscompilation:
90             resources.append(get_resource(context, bundle.csscompilation))
91 
92     fi = StringIO()
93     for script in resources:
94         fi.write(script + '\n')
95     folder.writeFile(meta_bundle + ".css", fi)
96 
97 
98 def get_override_directory(context):
99     persistent_directory = queryUtility(IResourceDirectory, name="persistent")
100     if persistent_directory is None:
101         return
102     if OVERRIDE_RESOURCE_DIRECTORY_NAME not in persistent_directory:
103         persistent_directory.makeDirectory(OVERRIDE_RESOURCE_DIRECTORY_NAME)
104     return persistent_directory[OVERRIDE_RESOURCE_DIRECTORY_NAME]
105 
106 
107 def combine_bundles(context):
108     container = get_override_directory(context)
109     if PRODUCTION_RESOURCE_DIRECTORY not in container:
110         container.makeDirectory(PRODUCTION_RESOURCE_DIRECTORY)
111     production_folder = container[PRODUCTION_RESOURCE_DIRECTORY]
112 
113     # store timestamp
114     fi = StringIO()
115     fi.write(datetime.now().isoformat())
116     production_folder.writeFile("timestamp.txt", fi)
117 
118     # generate new combined bundles
119     write_js(context, production_folder, 'default')
120     write_js(context, production_folder, 'logged-in')
121     write_css(context, production_folder, 'default')
122     write_css(context, production_folder, 'logged-in')
123
```
--- END FILES ---

Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.

Here is an example:

```diff
diff --git a/examples/server_async.py b/examples/server_async.py
--- a/examples/server_async.py
+++ b/examples/server_async.py
@@ -313,4 +313,4 @@
 
 
 if __name__ == "__main__":
-    asyncio.run(run_async_server("."), debug=True)
+    asyncio.run(run_async_server(), debug=True)
diff --git a/examples/server_sync.py b/examples/server_sync.py
--- a/examples/server_sync.py
+++ b/examples/server_sync.py
@@ -313,5 +313,5 @@
 
 
 if __name__ == "__main__":
-    server = run_sync_server(".")
+    server = run_sync_server()
     server.shutdown()

```

diff --git a/Products/CMFPlone/resources/browser/combine.py b/Products/CMFPlone/resources/browser/combine.py
--- a/Products/CMFPlone/resources/browser/combine.py
+++ b/Products/CMFPlone/resources/browser/combine.py
@@ -1,18 +1,20 @@
-from zExceptions import NotFound
 from Acquisition import aq_base
 from datetime import datetime
 from plone.registry.interfaces import IRegistry
 from plone.resource.file import FilesystemFile
 from plone.resource.interfaces import IResourceDirectory
 from Products.CMFPlone.interfaces import IBundleRegistry
-from Products.CMFPlone.interfaces.resources import (
-    OVERRIDE_RESOURCE_DIRECTORY_NAME,
-)
+from Products.CMFPlone.interfaces.resources import OVERRIDE_RESOURCE_DIRECTORY_NAME  # noqa
 from StringIO import StringIO
+from zExceptions import NotFound
 from zope.component import getUtility
 from zope.component import queryUtility
 
+import logging
+import re
+
 PRODUCTION_RESOURCE_DIRECTORY = "production"
+logger = logging.getLogger(__name__)
 
 
 def get_production_resource_directory():
@@ -24,6 +26,8 @@
         production_folder = container[PRODUCTION_RESOURCE_DIRECTORY]
     except NotFound:
         return "%s/++unique++1" % PRODUCTION_RESOURCE_DIRECTORY
+    if 'timestamp.txt' not in production_folder:
+        return "%s/++unique++1" % PRODUCTION_RESOURCE_DIRECTORY
     timestamp = production_folder.readFile('timestamp.txt')
     return "%s/++unique++%s" % (
         PRODUCTION_RESOURCE_DIRECTORY, timestamp)
@@ -38,7 +42,12 @@
         if overrides.isFile(filepath):
             return overrides.readFile(filepath)
 
-    resource = context.unrestrictedTraverse(path)
+    try:
+        resource = context.unrestrictedTraverse(path)
+    except NotFound:
+        logger.warn(u"Could not find resource {0}. You may have to create it first.".format(path))  # noqa
+        return
+
     if isinstance(resource, FilesystemFile):
         (directory, sep, filename) = path.rpartition('/')
         return context.unrestrictedTraverse(directory).readFile(filename)
@@ -71,7 +80,10 @@
         IBundleRegistry, prefix="plone.bundles", check=False)
     for bundle in bundles.values():
         if bundle.merge_with == meta_bundle and bundle.jscompilation:
-            resources.append(get_resource(context, bundle.jscompilation))
+            resource = get_resource(context, bundle.jscompilation)
+            if not resource:
+                continue
+            resources.append(resource)
 
     fi = StringIO()
     for script in resources:
@@ -87,7 +99,18 @@
         IBundleRegistry, prefix="plone.bundles", check=False)
     for bundle in bundles.values():
         if bundle.merge_with == meta_bundle and bundle.csscompilation:
-            resources.append(get_resource(context, bundle.csscompilation))
+            css = get_resource(context, bundle.csscompilation)
+            if not css:
+                continue
+            (path, sep, filename) = bundle.csscompilation.rpartition('/')
+            # Process relative urls:
+            # we prefix with current resource path any url not starting with
+            # '/' or http: or data:
+            css = re.sub(
+                r"""(url\(['"]?(?!['"]?([a-z]+:|\/)))""",
+                r'\1%s/' % path,
+                css)
+            resources.append(css)
 
     fi = StringIO()
     for script in resources:

{"golden_diff": "diff --git a/Products/CMFPlone/resources/browser/combine.py b/Products/CMFPlone/resources/browser/combine.py\n--- a/Products/CMFPlone/resources/browser/combine.py\n+++ b/Products/CMFPlone/resources/browser/combine.py\n@@ -1,18 +1,20 @@\n-from zExceptions import NotFound\n from Acquisition import aq_base\n from datetime import datetime\n from plone.registry.interfaces import IRegistry\n from plone.resource.file import FilesystemFile\n from plone.resource.interfaces import IResourceDirectory\n from Products.CMFPlone.interfaces import IBundleRegistry\n-from Products.CMFPlone.interfaces.resources import (\n-    OVERRIDE_RESOURCE_DIRECTORY_NAME,\n-)\n+from Products.CMFPlone.interfaces.resources import OVERRIDE_RESOURCE_DIRECTORY_NAME  # noqa\n from StringIO import StringIO\n+from zExceptions import NotFound\n from zope.component import getUtility\n from zope.component import queryUtility\n \n+import logging\n+import re\n+\n PRODUCTION_RESOURCE_DIRECTORY = \"production\"\n+logger = logging.getLogger(__name__)\n \n \n def get_production_resource_directory():\n@@ -24,6 +26,8 @@\n         production_folder = container[PRODUCTION_RESOURCE_DIRECTORY]\n     except NotFound:\n         return \"%s/++unique++1\" % PRODUCTION_RESOURCE_DIRECTORY\n+    if 'timestamp.txt' not in production_folder:\n+        return \"%s/++unique++1\" % PRODUCTION_RESOURCE_DIRECTORY\n     timestamp = production_folder.readFile('timestamp.txt')\n     return \"%s/++unique++%s\" % (\n         PRODUCTION_RESOURCE_DIRECTORY, timestamp)\n@@ -38,7 +42,12 @@\n         if overrides.isFile(filepath):\n             return overrides.readFile(filepath)\n \n-    resource = context.unrestrictedTraverse(path)\n+    try:\n+        resource = context.unrestrictedTraverse(path)\n+    except NotFound:\n+        logger.warn(u\"Could not find resource {0}. You may have to create it first.\".format(path))  # noqa\n+        return\n+\n     if isinstance(resource, FilesystemFile):\n         (directory, sep, filename) = path.rpartition('/')\n         return context.unrestrictedTraverse(directory).readFile(filename)\n@@ -71,7 +80,10 @@\n         IBundleRegistry, prefix=\"plone.bundles\", check=False)\n     for bundle in bundles.values():\n         if bundle.merge_with == meta_bundle and bundle.jscompilation:\n-            resources.append(get_resource(context, bundle.jscompilation))\n+            resource = get_resource(context, bundle.jscompilation)\n+            if not resource:\n+                continue\n+            resources.append(resource)\n \n     fi = StringIO()\n     for script in resources:\n@@ -87,7 +99,18 @@\n         IBundleRegistry, prefix=\"plone.bundles\", check=False)\n     for bundle in bundles.values():\n         if bundle.merge_with == meta_bundle and bundle.csscompilation:\n-            resources.append(get_resource(context, bundle.csscompilation))\n+            css = get_resource(context, bundle.csscompilation)\n+            if not css:\n+                continue\n+            (path, sep, filename) = bundle.csscompilation.rpartition('/')\n+            # Process relative urls:\n+            # we prefix with current resource path any url not starting with\n+            # '/' or http: or data:\n+            css = re.sub(\n+                r\"\"\"(url\\(['\"]?(?!['\"]?([a-z]+:|\\/)))\"\"\",\n+                r'\\1%s/' % path,\n+                css)\n+            resources.append(css)\n \n     fi = StringIO()\n     for script in resources:\n", "issue": "CSS bundles generation breaks background images relative urls\nThis is a bug related to PR #1300.\n\n", "before_files": [{"content": "from zExceptions import NotFound\nfrom Acquisition import aq_base\nfrom datetime import datetime\nfrom plone.registry.interfaces import IRegistry\nfrom plone.resource.file import FilesystemFile\nfrom plone.resource.interfaces import IResourceDirectory\nfrom Products.CMFPlone.interfaces import IBundleRegistry\nfrom Products.CMFPlone.interfaces.resources import (\n    OVERRIDE_RESOURCE_DIRECTORY_NAME,\n)\nfrom StringIO import StringIO\nfrom zope.component import getUtility\nfrom zope.component import queryUtility\n\nPRODUCTION_RESOURCE_DIRECTORY = \"production\"\n\n\ndef get_production_resource_directory():\n    persistent_directory = queryUtility(IResourceDirectory, name=\"persistent\")\n    if persistent_directory is None:\n        return ''\n    container = persistent_directory[OVERRIDE_RESOURCE_DIRECTORY_NAME]\n    try:\n        production_folder = container[PRODUCTION_RESOURCE_DIRECTORY]\n    except NotFound:\n        return \"%s/++unique++1\" % PRODUCTION_RESOURCE_DIRECTORY\n    timestamp = production_folder.readFile('timestamp.txt')\n    return \"%s/++unique++%s\" % (\n        PRODUCTION_RESOURCE_DIRECTORY, timestamp)\n\n\ndef get_resource(context, path):\n    if path.startswith('++plone++'):\n        # ++plone++ resources can be customized, we return their override\n        # value if any\n        overrides = get_override_directory(context)\n        filepath = path[9:]\n        if overrides.isFile(filepath):\n            return overrides.readFile(filepath)\n\n    resource = context.unrestrictedTraverse(path)\n    if isinstance(resource, FilesystemFile):\n        (directory, sep, filename) = path.rpartition('/')\n        return context.unrestrictedTraverse(directory).readFile(filename)\n    else:\n        if hasattr(aq_base(resource), 'GET'):\n            # for FileResource\n            return resource.GET()\n        else:\n            # any BrowserView\n            return resource()\n\n\ndef write_js(context, folder, meta_bundle):\n    registry = getUtility(IRegistry)\n    resources = []\n\n    # default resources\n    if meta_bundle == 'default' and registry.records.get(\n        'plone.resources/jquery.js'\n    ):\n        resources.append(get_resource(context,\n            registry.records['plone.resources/jquery.js'].value))\n        resources.append(get_resource(context,\n            registry.records['plone.resources.requirejs'].value))\n        resources.append(get_resource(context,\n            registry.records['plone.resources.configjs'].value))\n\n    # bundles\n    bundles = registry.collectionOfInterface(\n        IBundleRegistry, prefix=\"plone.bundles\", check=False)\n    for bundle in bundles.values():\n        if bundle.merge_with == meta_bundle and bundle.jscompilation:\n            resources.append(get_resource(context, bundle.jscompilation))\n\n    fi = StringIO()\n    for script in resources:\n        fi.write(script + '\\n')\n    folder.writeFile(meta_bundle + \".js\", fi)\n\n\ndef write_css(context, folder, meta_bundle):\n    registry = getUtility(IRegistry)\n    resources = []\n\n    bundles = registry.collectionOfInterface(\n        IBundleRegistry, prefix=\"plone.bundles\", check=False)\n    for bundle in bundles.values():\n        if bundle.merge_with == meta_bundle and bundle.csscompilation:\n            resources.append(get_resource(context, bundle.csscompilation))\n\n    fi = StringIO()\n    for script in resources:\n        fi.write(script + '\\n')\n    folder.writeFile(meta_bundle + \".css\", fi)\n\n\ndef get_override_directory(context):\n    persistent_directory = queryUtility(IResourceDirectory, name=\"persistent\")\n    if persistent_directory is None:\n        return\n    if OVERRIDE_RESOURCE_DIRECTORY_NAME not in persistent_directory:\n        persistent_directory.makeDirectory(OVERRIDE_RESOURCE_DIRECTORY_NAME)\n    return persistent_directory[OVERRIDE_RESOURCE_DIRECTORY_NAME]\n\n\ndef combine_bundles(context):\n    container = get_override_directory(context)\n    if PRODUCTION_RESOURCE_DIRECTORY not in container:\n        container.makeDirectory(PRODUCTION_RESOURCE_DIRECTORY)\n    production_folder = container[PRODUCTION_RESOURCE_DIRECTORY]\n\n    # store timestamp\n    fi = StringIO()\n    fi.write(datetime.now().isoformat())\n    production_folder.writeFile(\"timestamp.txt\", fi)\n\n    # generate new combined bundles\n    write_js(context, production_folder, 'default')\n    write_js(context, production_folder, 'logged-in')\n    write_css(context, production_folder, 'default')\n    write_css(context, production_folder, 'logged-in')\n", "path": "Products/CMFPlone/resources/browser/combine.py"}], "after_files": [{"content": "from Acquisition import aq_base\nfrom datetime import datetime\nfrom plone.registry.interfaces import IRegistry\nfrom plone.resource.file import FilesystemFile\nfrom plone.resource.interfaces import IResourceDirectory\nfrom Products.CMFPlone.interfaces import IBundleRegistry\nfrom Products.CMFPlone.interfaces.resources import OVERRIDE_RESOURCE_DIRECTORY_NAME  # noqa\nfrom StringIO import StringIO\nfrom zExceptions import NotFound\nfrom zope.component import getUtility\nfrom zope.component import queryUtility\n\nimport logging\nimport re\n\nPRODUCTION_RESOURCE_DIRECTORY = \"production\"\nlogger = logging.getLogger(__name__)\n\n\ndef get_production_resource_directory():\n    persistent_directory = queryUtility(IResourceDirectory, name=\"persistent\")\n    if persistent_directory is None:\n        return ''\n    container = persistent_directory[OVERRIDE_RESOURCE_DIRECTORY_NAME]\n    try:\n        production_folder = container[PRODUCTION_RESOURCE_DIRECTORY]\n    except NotFound:\n        return \"%s/++unique++1\" % PRODUCTION_RESOURCE_DIRECTORY\n    if 'timestamp.txt' not in production_folder:\n        return \"%s/++unique++1\" % PRODUCTION_RESOURCE_DIRECTORY\n    timestamp = production_folder.readFile('timestamp.txt')\n    return \"%s/++unique++%s\" % (\n        PRODUCTION_RESOURCE_DIRECTORY, timestamp)\n\n\ndef get_resource(context, path):\n    if path.startswith('++plone++'):\n        # ++plone++ resources can be customized, we return their override\n        # value if any\n        overrides = get_override_directory(context)\n        filepath = path[9:]\n        if overrides.isFile(filepath):\n            return overrides.readFile(filepath)\n\n    try:\n        resource = context.unrestrictedTraverse(path)\n    except NotFound:\n        logger.warn(u\"Could not find resource {0}. You may have to create it first.\".format(path))  # noqa\n        return\n\n    if isinstance(resource, FilesystemFile):\n        (directory, sep, filename) = path.rpartition('/')\n        return context.unrestrictedTraverse(directory).readFile(filename)\n    else:\n        if hasattr(aq_base(resource), 'GET'):\n            # for FileResource\n            return resource.GET()\n        else:\n            # any BrowserView\n            return resource()\n\n\ndef write_js(context, folder, meta_bundle):\n    registry = getUtility(IRegistry)\n    resources = []\n\n    # default resources\n    if meta_bundle == 'default' and registry.records.get(\n        'plone.resources/jquery.js'\n    ):\n        resources.append(get_resource(context,\n            registry.records['plone.resources/jquery.js'].value))\n        resources.append(get_resource(context,\n            registry.records['plone.resources.requirejs'].value))\n        resources.append(get_resource(context,\n            registry.records['plone.resources.configjs'].value))\n\n    # bundles\n    bundles = registry.collectionOfInterface(\n        IBundleRegistry, prefix=\"plone.bundles\", check=False)\n    for bundle in bundles.values():\n        if bundle.merge_with == meta_bundle and bundle.jscompilation:\n            resource = get_resource(context, bundle.jscompilation)\n            if not resource:\n                continue\n            resources.append(resource)\n\n    fi = StringIO()\n    for script in resources:\n        fi.write(script + '\\n')\n    folder.writeFile(meta_bundle + \".js\", fi)\n\n\ndef write_css(context, folder, meta_bundle):\n    registry = getUtility(IRegistry)\n    resources = []\n\n    bundles = registry.collectionOfInterface(\n        IBundleRegistry, prefix=\"plone.bundles\", check=False)\n    for bundle in bundles.values():\n        if bundle.merge_with == meta_bundle and bundle.csscompilation:\n            css = get_resource(context, bundle.csscompilation)\n            if not css:\n                continue\n            (path, sep, filename) = bundle.csscompilation.rpartition('/')\n            # Process relative urls:\n            # we prefix with current resource path any url not starting with\n            # '/' or http: or data:\n            css = re.sub(\n                r\"\"\"(url\\(['\"]?(?!['\"]?([a-z]+:|\\/)))\"\"\",\n                r'\\1%s/' % path,\n                css)\n            resources.append(css)\n\n    fi = StringIO()\n    for script in resources:\n        fi.write(script + '\\n')\n    folder.writeFile(meta_bundle + \".css\", fi)\n\n\ndef get_override_directory(context):\n    persistent_directory = queryUtility(IResourceDirectory, name=\"persistent\")\n    if persistent_directory is None:\n        return\n    if OVERRIDE_RESOURCE_DIRECTORY_NAME not in persistent_directory:\n        persistent_directory.makeDirectory(OVERRIDE_RESOURCE_DIRECTORY_NAME)\n    return persistent_directory[OVERRIDE_RESOURCE_DIRECTORY_NAME]\n\n\ndef combine_bundles(context):\n    container = get_override_directory(context)\n    if PRODUCTION_RESOURCE_DIRECTORY not in container:\n        container.makeDirectory(PRODUCTION_RESOURCE_DIRECTORY)\n    production_folder = container[PRODUCTION_RESOURCE_DIRECTORY]\n\n    # store timestamp\n    fi = StringIO()\n    fi.write(datetime.now().isoformat())\n    production_folder.writeFile(\"timestamp.txt\", fi)\n\n    # generate new combined bundles\n    write_js(context, production_folder, 'default')\n    write_js(context, production_folder, 'logged-in')\n    write_css(context, production_folder, 'default')\n    write_css(context, production_folder, 'logged-in')\n", "path": "Products/CMFPlone/resources/browser/combine.py"}]}