prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  HTTP_PROXY variable with username and empty password not supported
  Scrapy doesn't support proxy authentication when the password is empty when using the HTTP_PROXY environment variable to supply the proxy argument.
  
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `scrapy/downloadermiddlewares/httpproxy.py`
  Content:
  ```
  1 import base64
  2 from six.moves.urllib.request import getproxies, proxy_bypass
  3 from six.moves.urllib.parse import unquote
  4 try:
  5     from urllib2 import _parse_proxy
  6 except ImportError:
  7     from urllib.request import _parse_proxy
  8 from six.moves.urllib.parse import urlunparse
  9 
  10 from scrapy.utils.httpobj import urlparse_cached
  11 from scrapy.exceptions import NotConfigured
  12 
  13 
  14 class HttpProxyMiddleware(object):
  15 
  16     def __init__(self):
  17         self.proxies = {}
  18         for type, url in getproxies().items():
  19             self.proxies[type] = self._get_proxy(url, type)
  20 
  21         if not self.proxies:
  22             raise NotConfigured
  23 
  24     def _get_proxy(self, url, orig_type):
  25         proxy_type, user, password, hostport = _parse_proxy(url)
  26         proxy_url = urlunparse((proxy_type or orig_type, hostport, '', '', '', ''))
  27 
  28         if user and password:
  29             user_pass = '%s:%s' % (unquote(user), unquote(password))
  30             creds = base64.b64encode(user_pass).strip()
  31         else:
  32             creds = None
  33 
  34         return creds, proxy_url
  35 
  36     def process_request(self, request, spider):
  37         # ignore if proxy is already seted
  38         if 'proxy' in request.meta:
  39             return
  40 
  41         parsed = urlparse_cached(request)
  42         scheme = parsed.scheme
  43 
  44         # 'no_proxy' is only supported by http schemes
  45         if scheme in ('http', 'https') and proxy_bypass(parsed.hostname):
  46             return
  47 
  48         if scheme in self.proxies:
  49             self._set_proxy(request, scheme)
  50 
  51     def _set_proxy(self, request, scheme):
  52         creds, proxy = self.proxies[scheme]
  53         request.meta['proxy'] = proxy
  54         if creds:
  55             request.headers['Proxy-Authorization'] = 'Basic ' + creds
  56
  ```
  --- 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/scrapy/downloadermiddlewares/httpproxy.py b/scrapy/downloadermiddlewares/httpproxy.py
  --- a/scrapy/downloadermiddlewares/httpproxy.py
  +++ b/scrapy/downloadermiddlewares/httpproxy.py
  @@ -25,7 +25,7 @@
           proxy_type, user, password, hostport = _parse_proxy(url)
           proxy_url = urlunparse((proxy_type or orig_type, hostport, '', '', '', ''))
   
  -        if user and password:
  +        if user:
               user_pass = '%s:%s' % (unquote(user), unquote(password))
               creds = base64.b64encode(user_pass).strip()
           else:
  
verification_info: {"golden_diff": "diff --git a/scrapy/downloadermiddlewares/httpproxy.py b/scrapy/downloadermiddlewares/httpproxy.py\n--- a/scrapy/downloadermiddlewares/httpproxy.py\n+++ b/scrapy/downloadermiddlewares/httpproxy.py\n@@ -25,7 +25,7 @@\n         proxy_type, user, password, hostport = _parse_proxy(url)\n         proxy_url = urlunparse((proxy_type or orig_type, hostport, '', '', '', ''))\n \n-        if user and password:\n+        if user:\n             user_pass = '%s:%s' % (unquote(user), unquote(password))\n             creds = base64.b64encode(user_pass).strip()\n         else:\n", "issue": "HTTP_PROXY variable with username and empty password not supported\nScrapy doesn't support proxy authentication when the password is empty when using the HTTP_PROXY environment variable to supply the proxy argument.\n\n", "before_files": [{"content": "import base64\nfrom six.moves.urllib.request import getproxies, proxy_bypass\nfrom six.moves.urllib.parse import unquote\ntry:\n    from urllib2 import _parse_proxy\nexcept ImportError:\n    from urllib.request import _parse_proxy\nfrom six.moves.urllib.parse import urlunparse\n\nfrom scrapy.utils.httpobj import urlparse_cached\nfrom scrapy.exceptions import NotConfigured\n\n\nclass HttpProxyMiddleware(object):\n\n    def __init__(self):\n        self.proxies = {}\n        for type, url in getproxies().items():\n            self.proxies[type] = self._get_proxy(url, type)\n\n        if not self.proxies:\n            raise NotConfigured\n\n    def _get_proxy(self, url, orig_type):\n        proxy_type, user, password, hostport = _parse_proxy(url)\n        proxy_url = urlunparse((proxy_type or orig_type, hostport, '', '', '', ''))\n\n        if user and password:\n            user_pass = '%s:%s' % (unquote(user), unquote(password))\n            creds = base64.b64encode(user_pass).strip()\n        else:\n            creds = None\n\n        return creds, proxy_url\n\n    def process_request(self, request, spider):\n        # ignore if proxy is already seted\n        if 'proxy' in request.meta:\n            return\n\n        parsed = urlparse_cached(request)\n        scheme = parsed.scheme\n\n        # 'no_proxy' is only supported by http schemes\n        if scheme in ('http', 'https') and proxy_bypass(parsed.hostname):\n            return\n\n        if scheme in self.proxies:\n            self._set_proxy(request, scheme)\n\n    def _set_proxy(self, request, scheme):\n        creds, proxy = self.proxies[scheme]\n        request.meta['proxy'] = proxy\n        if creds:\n            request.headers['Proxy-Authorization'] = 'Basic ' + creds\n", "path": "scrapy/downloadermiddlewares/httpproxy.py"}], "after_files": [{"content": "import base64\nfrom six.moves.urllib.request import getproxies, proxy_bypass\nfrom six.moves.urllib.parse import unquote\ntry:\n    from urllib2 import _parse_proxy\nexcept ImportError:\n    from urllib.request import _parse_proxy\nfrom six.moves.urllib.parse import urlunparse\n\nfrom scrapy.utils.httpobj import urlparse_cached\nfrom scrapy.exceptions import NotConfigured\n\n\nclass HttpProxyMiddleware(object):\n\n    def __init__(self):\n        self.proxies = {}\n        for type, url in getproxies().items():\n            self.proxies[type] = self._get_proxy(url, type)\n\n        if not self.proxies:\n            raise NotConfigured\n\n    def _get_proxy(self, url, orig_type):\n        proxy_type, user, password, hostport = _parse_proxy(url)\n        proxy_url = urlunparse((proxy_type or orig_type, hostport, '', '', '', ''))\n\n        if user:\n            user_pass = '%s:%s' % (unquote(user), unquote(password))\n            creds = base64.b64encode(user_pass).strip()\n        else:\n            creds = None\n\n        return creds, proxy_url\n\n    def process_request(self, request, spider):\n        # ignore if proxy is already seted\n        if 'proxy' in request.meta:\n            return\n\n        parsed = urlparse_cached(request)\n        scheme = parsed.scheme\n\n        # 'no_proxy' is only supported by http schemes\n        if scheme in ('http', 'https') and proxy_bypass(parsed.hostname):\n            return\n\n        if scheme in self.proxies:\n            self._set_proxy(request, scheme)\n\n    def _set_proxy(self, request, scheme):\n        creds, proxy = self.proxies[scheme]\n        request.meta['proxy'] = proxy\n        if creds:\n            request.headers['Proxy-Authorization'] = 'Basic ' + creds\n", "path": "scrapy/downloadermiddlewares/httpproxy.py"}]}