old_contents: import os
  import pytest
  import threading
  import requests
  
  from tests.testserver.server import Server
  
  from .utils import override_environ
  
  
  def test_chunked_upload():
      """can safely send generators"""
      close_server = threading.Event()
      server = Server.basic_response_server(wait_to_close_event=close_server)
      data = (i for i in [b'a', b'b', b'c'])
  
      with server as (host, port):
          url = 'http://{0}:{1}/'.format(host, port)
          r = requests.post(url, data=data, stream=True)
          close_server.set() # release server block
  
      assert r.status_code == 200
      assert r.request.headers['Transfer-Encoding'] == 'chunked'
  
  
  _schemes_by_var_prefix = [
      ('http', ['http']),
      ('https', ['https']),
      ('all', ['http', 'https']),
  ]
  
  _proxy_combos = []
  for prefix, schemes in _schemes_by_var_prefix:
      for scheme in schemes:
          _proxy_combos.append(("{0}_proxy".format(prefix), scheme))
  
  _proxy_combos += [(var.upper(), scheme) for var, scheme in _proxy_combos]
  
  
  @pytest.mark.parametrize("var,scheme", _proxy_combos)
  def test_use_proxy_from_environment(httpbin, var, scheme):
      url = "{0}://httpbin.org".format(scheme)
      fake_proxy = Server()  # do nothing with the requests; just close the socket
      with fake_proxy as (host, port):
          proxy_url = "socks5://{0}:{1}".format(host, port)
          kwargs = {var: proxy_url}
          with override_environ(**kwargs):
              # fake proxy's lack of response will cause a ConnectionError
              with pytest.raises(requests.exceptions.ConnectionError):
                  requests.get(url)
  
          # the fake proxy received a request
          assert len(fake_proxy.handler_results) == 1
  
          # it had actual content (not checking for SOCKS protocol for now)
          assert len(fake_proxy.handler_results[0]) > 0
  
new_contents: import os
  import pytest
  import threading
  import requests
  
  from tests.testserver.server import Server
  
  from .utils import override_environ
  
  
  def test_chunked_upload():
      """can safely send generators"""
      close_server = threading.Event()
      server = Server.basic_response_server(wait_to_close_event=close_server)
      data = iter([b'a', b'b', b'c'])
  
      with server as (host, port):
          url = 'http://{0}:{1}/'.format(host, port)
          r = requests.post(url, data=data, stream=True)
          close_server.set() # release server block
  
      assert r.status_code == 200
      assert r.request.headers['Transfer-Encoding'] == 'chunked'
  
  
  _schemes_by_var_prefix = [
      ('http', ['http']),
      ('https', ['https']),
      ('all', ['http', 'https']),
  ]
  
  _proxy_combos = []
  for prefix, schemes in _schemes_by_var_prefix:
      for scheme in schemes:
          _proxy_combos.append(("{0}_proxy".format(prefix), scheme))
  
  _proxy_combos += [(var.upper(), scheme) for var, scheme in _proxy_combos]
  
  
  @pytest.mark.parametrize("var,scheme", _proxy_combos)
  def test_use_proxy_from_environment(httpbin, var, scheme):
      url = "{0}://httpbin.org".format(scheme)
      fake_proxy = Server()  # do nothing with the requests; just close the socket
      with fake_proxy as (host, port):
          proxy_url = "socks5://{0}:{1}".format(host, port)
          kwargs = {var: proxy_url}
          with override_environ(**kwargs):
              # fake proxy's lack of response will cause a ConnectionError
              with pytest.raises(requests.exceptions.ConnectionError):
                  requests.get(url)
  
          # the fake proxy received a request
          assert len(fake_proxy.handler_results) == 1
  
          # it had actual content (not checking for SOCKS protocol for now)
          assert len(fake_proxy.handler_results[0]) > 0
  
subject: Use iter instead of noop list comprehension