prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  render fails if the theme has a code.css  
  The `conf.py` says: 
  
  ```
  # Color scheme to be used for code blocks. If your theme provides
  # "assets/css/code.css" this is ignored.
  ```
  
  I've [provided one](https://github.com/mgaitan/my-nikola-theme/commit/f0140d0d67771d7ee9f46df2c78548c0e757f65e) but then I can't render my site
  
  ```
  (blog)tin@morochita:~/lab/blog$ nikola build
  Scanning posts.....done!
  ERROR: Two different tasks can't have a common target.'output/assets/css/code.css' is a target for copy_files:output/assets/css/code.css and copy_assets:output/assets/css/code.css.
  (blog)tin@morochita:~/lab/blog$ 
  ```
  
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `nikola/plugins/task/copy_assets.py`
  Content:
  ```
  1 # -*- coding: utf-8 -*-
  2 
  3 # Copyright © 2012-2014 Roberto Alsina and others.
  4 
  5 # Permission is hereby granted, free of charge, to any
  6 # person obtaining a copy of this software and associated
  7 # documentation files (the "Software"), to deal in the
  8 # Software without restriction, including without limitation
  9 # the rights to use, copy, modify, merge, publish,
  10 # distribute, sublicense, and/or sell copies of the
  11 # Software, and to permit persons to whom the Software is
  12 # furnished to do so, subject to the following conditions:
  13 #
  14 # The above copyright notice and this permission notice
  15 # shall be included in all copies or substantial portions of
  16 # the Software.
  17 #
  18 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
  19 # KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
  20 # WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
  21 # PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
  22 # OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  23 # OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  24 # OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  25 # SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  26 
  27 import codecs
  28 import os
  29 
  30 from nikola.plugin_categories import Task
  31 from nikola import utils
  32 
  33 
  34 class CopyAssets(Task):
  35     """Copy theme assets into output."""
  36 
  37     name = "copy_assets"
  38 
  39     def gen_tasks(self):
  40         """Create tasks to copy the assets of the whole theme chain.
  41 
  42         If a file is present on two themes, use the version
  43         from the "youngest" theme.
  44         """
  45 
  46         kw = {
  47             "themes": self.site.THEMES,
  48             "output_folder": self.site.config['OUTPUT_FOLDER'],
  49             "filters": self.site.config['FILTERS'],
  50             "code_color_scheme": self.site.config['CODE_COLOR_SCHEME'],
  51             "code.css_selectors": 'pre.code',
  52             "code.css_close": "\ntable.codetable { width: 100%;} td.linenos {text-align: right; width: 4em;}\n",
  53         }
  54         has_code_css = False
  55         tasks = {}
  56         code_css_path = os.path.join(kw['output_folder'], 'assets', 'css', 'code.css')
  57 
  58         yield self.group_task()
  59 
  60         for theme_name in kw['themes']:
  61             src = os.path.join(utils.get_theme_path(theme_name), 'assets')
  62             dst = os.path.join(kw['output_folder'], 'assets')
  63             for task in utils.copy_tree(src, dst):
  64                 if task['name'] in tasks:
  65                     continue
  66                 has_code_css = task['targets'][0] == code_css_path
  67                 tasks[task['name']] = task
  68                 task['uptodate'] = [utils.config_changed(kw)]
  69                 task['basename'] = self.name
  70                 yield utils.apply_filters(task, kw['filters'])
  71 
  72         if not has_code_css:  # Generate it
  73 
  74             def create_code_css():
  75                 from pygments.formatters import get_formatter_by_name
  76                 formatter = get_formatter_by_name('html', style=kw["code_color_scheme"])
  77                 utils.makedirs(os.path.dirname(code_css_path))
  78                 with codecs.open(code_css_path, 'wb+', 'utf8') as outf:
  79                     outf.write(formatter.get_style_defs(kw["code.css_selectors"]))
  80                     outf.write(kw["code.css_close"])
  81 
  82             task = {
  83                 'basename': self.name,
  84                 'name': code_css_path,
  85                 'targets': [code_css_path],
  86                 'uptodate': [utils.config_changed(kw)],
  87                 'actions': [(create_code_css, [])],
  88                 'clean': True,
  89             }
  90             yield utils.apply_filters(task, kw['filters'])
  91
  ```
  --- 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()
  
  ```
  
golden_diff: diff --git a/nikola/plugins/task/copy_assets.py b/nikola/plugins/task/copy_assets.py
  --- a/nikola/plugins/task/copy_assets.py
  +++ b/nikola/plugins/task/copy_assets.py
  @@ -45,15 +45,21 @@
   
           kw = {
               "themes": self.site.THEMES,
  +            "files_folders": self.site.config['FILES_FOLDERS'],
               "output_folder": self.site.config['OUTPUT_FOLDER'],
               "filters": self.site.config['FILTERS'],
               "code_color_scheme": self.site.config['CODE_COLOR_SCHEME'],
               "code.css_selectors": 'pre.code',
  +            "code.css_head": '/* code.css file generated by Nikola */\n',
               "code.css_close": "\ntable.codetable { width: 100%;} td.linenos {text-align: right; width: 4em;}\n",
           }
  -        has_code_css = False
           tasks = {}
           code_css_path = os.path.join(kw['output_folder'], 'assets', 'css', 'code.css')
  +        code_css_input = utils.get_asset_path('assets/css/code.css',
  +                                              themes=kw['themes'],
  +                                              files_folders=kw['files_folders'])
  +
  +        kw["code.css_input"] = code_css_input
   
           yield self.group_task()
   
  @@ -63,27 +69,35 @@
               for task in utils.copy_tree(src, dst):
                   if task['name'] in tasks:
                       continue
  -                has_code_css = task['targets'][0] == code_css_path
                   tasks[task['name']] = task
                   task['uptodate'] = [utils.config_changed(kw)]
                   task['basename'] = self.name
  +                if code_css_input:
  +                    task['file_dep'] = [code_css_input]
                   yield utils.apply_filters(task, kw['filters'])
   
  -        if not has_code_css:  # Generate it
  -
  +        # Check whether or not there is a code.css file around.
  +        if not code_css_input:
               def create_code_css():
                   from pygments.formatters import get_formatter_by_name
                   formatter = get_formatter_by_name('html', style=kw["code_color_scheme"])
                   utils.makedirs(os.path.dirname(code_css_path))
                   with codecs.open(code_css_path, 'wb+', 'utf8') as outf:
  +                    outf.write(kw["code.css_head"])
                       outf.write(formatter.get_style_defs(kw["code.css_selectors"]))
                       outf.write(kw["code.css_close"])
   
  +            if os.path.exists(code_css_path):
  +                with codecs.open(code_css_path, 'r', 'utf-8') as fh:
  +                    testcontents = fh.read(len(kw["code.css_head"])) == kw["code.css_head"]
  +            else:
  +                testcontents = False
  +
               task = {
                   'basename': self.name,
                   'name': code_css_path,
                   'targets': [code_css_path],
  -                'uptodate': [utils.config_changed(kw)],
  +                'uptodate': [utils.config_changed(kw), testcontents],
                   'actions': [(create_code_css, [])],
                   'clean': True,
               }
  
verification_info: {"golden_diff": "diff --git a/nikola/plugins/task/copy_assets.py b/nikola/plugins/task/copy_assets.py\n--- a/nikola/plugins/task/copy_assets.py\n+++ b/nikola/plugins/task/copy_assets.py\n@@ -45,15 +45,21 @@\n \n         kw = {\n             \"themes\": self.site.THEMES,\n+            \"files_folders\": self.site.config['FILES_FOLDERS'],\n             \"output_folder\": self.site.config['OUTPUT_FOLDER'],\n             \"filters\": self.site.config['FILTERS'],\n             \"code_color_scheme\": self.site.config['CODE_COLOR_SCHEME'],\n             \"code.css_selectors\": 'pre.code',\n+            \"code.css_head\": '/* code.css file generated by Nikola */\\n',\n             \"code.css_close\": \"\\ntable.codetable { width: 100%;} td.linenos {text-align: right; width: 4em;}\\n\",\n         }\n-        has_code_css = False\n         tasks = {}\n         code_css_path = os.path.join(kw['output_folder'], 'assets', 'css', 'code.css')\n+        code_css_input = utils.get_asset_path('assets/css/code.css',\n+                                              themes=kw['themes'],\n+                                              files_folders=kw['files_folders'])\n+\n+        kw[\"code.css_input\"] = code_css_input\n \n         yield self.group_task()\n \n@@ -63,27 +69,35 @@\n             for task in utils.copy_tree(src, dst):\n                 if task['name'] in tasks:\n                     continue\n-                has_code_css = task['targets'][0] == code_css_path\n                 tasks[task['name']] = task\n                 task['uptodate'] = [utils.config_changed(kw)]\n                 task['basename'] = self.name\n+                if code_css_input:\n+                    task['file_dep'] = [code_css_input]\n                 yield utils.apply_filters(task, kw['filters'])\n \n-        if not has_code_css:  # Generate it\n-\n+        # Check whether or not there is a code.css file around.\n+        if not code_css_input:\n             def create_code_css():\n                 from pygments.formatters import get_formatter_by_name\n                 formatter = get_formatter_by_name('html', style=kw[\"code_color_scheme\"])\n                 utils.makedirs(os.path.dirname(code_css_path))\n                 with codecs.open(code_css_path, 'wb+', 'utf8') as outf:\n+                    outf.write(kw[\"code.css_head\"])\n                     outf.write(formatter.get_style_defs(kw[\"code.css_selectors\"]))\n                     outf.write(kw[\"code.css_close\"])\n \n+            if os.path.exists(code_css_path):\n+                with codecs.open(code_css_path, 'r', 'utf-8') as fh:\n+                    testcontents = fh.read(len(kw[\"code.css_head\"])) == kw[\"code.css_head\"]\n+            else:\n+                testcontents = False\n+\n             task = {\n                 'basename': self.name,\n                 'name': code_css_path,\n                 'targets': [code_css_path],\n-                'uptodate': [utils.config_changed(kw)],\n+                'uptodate': [utils.config_changed(kw), testcontents],\n                 'actions': [(create_code_css, [])],\n                 'clean': True,\n             }\n", "issue": "render fails if the theme has a code.css  \nThe `conf.py` says: \n\n```\n# Color scheme to be used for code blocks. If your theme provides\n# \"assets/css/code.css\" this is ignored.\n```\n\nI've [provided one](https://github.com/mgaitan/my-nikola-theme/commit/f0140d0d67771d7ee9f46df2c78548c0e757f65e) but then I can't render my site\n\n```\n(blog)tin@morochita:~/lab/blog$ nikola build\nScanning posts.....done!\nERROR: Two different tasks can't have a common target.'output/assets/css/code.css' is a target for copy_files:output/assets/css/code.css and copy_assets:output/assets/css/code.css.\n(blog)tin@morochita:~/lab/blog$ \n```\n\n", "before_files": [{"content": "# -*- coding: utf-8 -*-\n\n# Copyright \u00a9 2012-2014 Roberto Alsina and others.\n\n# Permission is hereby granted, free of charge, to any\n# person obtaining a copy of this software and associated\n# documentation files (the \"Software\"), to deal in the\n# Software without restriction, including without limitation\n# the rights to use, copy, modify, merge, publish,\n# distribute, sublicense, and/or sell copies of the\n# Software, and to permit persons to whom the Software is\n# furnished to do so, subject to the following conditions:\n#\n# The above copyright notice and this permission notice\n# shall be included in all copies or substantial portions of\n# the Software.\n#\n# THE SOFTWARE IS PROVIDED \"AS IS\", WITHOUT WARRANTY OF ANY\n# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE\n# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR\n# PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS\n# OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR\n# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR\n# OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE\n# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.\n\nimport codecs\nimport os\n\nfrom nikola.plugin_categories import Task\nfrom nikola import utils\n\n\nclass CopyAssets(Task):\n    \"\"\"Copy theme assets into output.\"\"\"\n\n    name = \"copy_assets\"\n\n    def gen_tasks(self):\n        \"\"\"Create tasks to copy the assets of the whole theme chain.\n\n        If a file is present on two themes, use the version\n        from the \"youngest\" theme.\n        \"\"\"\n\n        kw = {\n            \"themes\": self.site.THEMES,\n            \"output_folder\": self.site.config['OUTPUT_FOLDER'],\n            \"filters\": self.site.config['FILTERS'],\n            \"code_color_scheme\": self.site.config['CODE_COLOR_SCHEME'],\n            \"code.css_selectors\": 'pre.code',\n            \"code.css_close\": \"\\ntable.codetable { width: 100%;} td.linenos {text-align: right; width: 4em;}\\n\",\n        }\n        has_code_css = False\n        tasks = {}\n        code_css_path = os.path.join(kw['output_folder'], 'assets', 'css', 'code.css')\n\n        yield self.group_task()\n\n        for theme_name in kw['themes']:\n            src = os.path.join(utils.get_theme_path(theme_name), 'assets')\n            dst = os.path.join(kw['output_folder'], 'assets')\n            for task in utils.copy_tree(src, dst):\n                if task['name'] in tasks:\n                    continue\n                has_code_css = task['targets'][0] == code_css_path\n                tasks[task['name']] = task\n                task['uptodate'] = [utils.config_changed(kw)]\n                task['basename'] = self.name\n                yield utils.apply_filters(task, kw['filters'])\n\n        if not has_code_css:  # Generate it\n\n            def create_code_css():\n                from pygments.formatters import get_formatter_by_name\n                formatter = get_formatter_by_name('html', style=kw[\"code_color_scheme\"])\n                utils.makedirs(os.path.dirname(code_css_path))\n                with codecs.open(code_css_path, 'wb+', 'utf8') as outf:\n                    outf.write(formatter.get_style_defs(kw[\"code.css_selectors\"]))\n                    outf.write(kw[\"code.css_close\"])\n\n            task = {\n                'basename': self.name,\n                'name': code_css_path,\n                'targets': [code_css_path],\n                'uptodate': [utils.config_changed(kw)],\n                'actions': [(create_code_css, [])],\n                'clean': True,\n            }\n            yield utils.apply_filters(task, kw['filters'])\n", "path": "nikola/plugins/task/copy_assets.py"}], "after_files": [{"content": "# -*- coding: utf-8 -*-\n\n# Copyright \u00a9 2012-2014 Roberto Alsina and others.\n\n# Permission is hereby granted, free of charge, to any\n# person obtaining a copy of this software and associated\n# documentation files (the \"Software\"), to deal in the\n# Software without restriction, including without limitation\n# the rights to use, copy, modify, merge, publish,\n# distribute, sublicense, and/or sell copies of the\n# Software, and to permit persons to whom the Software is\n# furnished to do so, subject to the following conditions:\n#\n# The above copyright notice and this permission notice\n# shall be included in all copies or substantial portions of\n# the Software.\n#\n# THE SOFTWARE IS PROVIDED \"AS IS\", WITHOUT WARRANTY OF ANY\n# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE\n# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR\n# PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS\n# OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR\n# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR\n# OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE\n# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.\n\nimport codecs\nimport os\n\nfrom nikola.plugin_categories import Task\nfrom nikola import utils\n\n\nclass CopyAssets(Task):\n    \"\"\"Copy theme assets into output.\"\"\"\n\n    name = \"copy_assets\"\n\n    def gen_tasks(self):\n        \"\"\"Create tasks to copy the assets of the whole theme chain.\n\n        If a file is present on two themes, use the version\n        from the \"youngest\" theme.\n        \"\"\"\n\n        kw = {\n            \"themes\": self.site.THEMES,\n            \"files_folders\": self.site.config['FILES_FOLDERS'],\n            \"output_folder\": self.site.config['OUTPUT_FOLDER'],\n            \"filters\": self.site.config['FILTERS'],\n            \"code_color_scheme\": self.site.config['CODE_COLOR_SCHEME'],\n            \"code.css_selectors\": 'pre.code',\n            \"code.css_head\": '/* code.css file generated by Nikola */\\n',\n            \"code.css_close\": \"\\ntable.codetable { width: 100%;} td.linenos {text-align: right; width: 4em;}\\n\",\n        }\n        tasks = {}\n        code_css_path = os.path.join(kw['output_folder'], 'assets', 'css', 'code.css')\n        code_css_input = utils.get_asset_path('assets/css/code.css',\n                                              themes=kw['themes'],\n                                              files_folders=kw['files_folders'])\n\n        kw[\"code.css_input\"] = code_css_input\n\n        yield self.group_task()\n\n        for theme_name in kw['themes']:\n            src = os.path.join(utils.get_theme_path(theme_name), 'assets')\n            dst = os.path.join(kw['output_folder'], 'assets')\n            for task in utils.copy_tree(src, dst):\n                if task['name'] in tasks:\n                    continue\n                tasks[task['name']] = task\n                task['uptodate'] = [utils.config_changed(kw)]\n                task['basename'] = self.name\n                if code_css_input:\n                    task['file_dep'] = [code_css_input]\n                yield utils.apply_filters(task, kw['filters'])\n\n        # Check whether or not there is a code.css file around.\n        if not code_css_input:\n            def create_code_css():\n                from pygments.formatters import get_formatter_by_name\n                formatter = get_formatter_by_name('html', style=kw[\"code_color_scheme\"])\n                utils.makedirs(os.path.dirname(code_css_path))\n                with codecs.open(code_css_path, 'wb+', 'utf8') as outf:\n                    outf.write(kw[\"code.css_head\"])\n                    outf.write(formatter.get_style_defs(kw[\"code.css_selectors\"]))\n                    outf.write(kw[\"code.css_close\"])\n\n            if os.path.exists(code_css_path):\n                with codecs.open(code_css_path, 'r', 'utf-8') as fh:\n                    testcontents = fh.read(len(kw[\"code.css_head\"])) == kw[\"code.css_head\"]\n            else:\n                testcontents = False\n\n            task = {\n                'basename': self.name,\n                'name': code_css_path,\n                'targets': [code_css_path],\n                'uptodate': [utils.config_changed(kw), testcontents],\n                'actions': [(create_code_css, [])],\n                'clean': True,\n            }\n            yield utils.apply_filters(task, kw['filters'])\n", "path": "nikola/plugins/task/copy_assets.py"}]}