added fix for edge case in pip.utils.find_command and moved `BadCommand` raise from `VersionControl.cmd` to `find_command`

pip/util.py

@@ -7,7 +7,7 @@ import posixpath
 import pkg_resources
 import zipfile
 import tarfile
-from pip.exceptions import InstallationError
+from pip.exceptions import InstallationError, BadCommand
 from pip.backwardcompat import WindowsError, string_types, raw_input
 from pip.locations import site_packages, running_under_virtualenv
 from pip.log import logger
@@ -71,7 +71,7 @@ def backup_dir(dir, ext='.bak'):
 def find_command(cmd, paths=None, pathext=None):
     """Searches the PATH for the given command and returns its path"""
     if paths is None:
-        paths = os.environ.get('PATH', []).split(os.pathsep)
+        paths = os.environ.get('PATH', '').split(os.pathsep)
     if isinstance(paths, string_types):
         paths = [paths]
     # check if there are funny path extensions for executables, e.g. Windows
@@ -92,7 +92,8 @@ def find_command(cmd, paths=None, pathext=None):
                 return cmd_path_ext
         if os.path.isfile(cmd_path):
             return cmd_path
-    return None
+    raise BadCommand('Cannot find command %r' % cmd)
+
 
 def get_pathext(default_pathext=None):
     """Returns the path extensions from environment or a default"""

pip/vcs/__init__.py

@@ -4,7 +4,6 @@ import os
 import shutil
 
 from pip.backwardcompat import urlparse, urllib
-from pip.exceptions import BadCommand
 from pip.log import logger
 from pip.util import display_path, backup_dir, find_command, ask, rmtree
 
@@ -106,8 +105,6 @@ class VersionControl(object):
         if self._cmd is not None:
             return self._cmd
         command = find_command(self.name)
-        if command is None:
-            raise BadCommand('Cannot find command %r' % self.name)
         logger.info('Found command %r at %r' % (self.name, command))
         self._cmd = command
         return command

tests/test_basic.py

@@ -9,6 +9,7 @@ from nose import SkipTest
 from mock import Mock, patch
 
 from pip.util import rmtree, find_command
+from pip.exceptions import BadCommand
 
 from tests.test_pip import (here, reset_env, run_pip, pyversion, mkdir,
                             src_folder, write_file)
@@ -525,6 +526,23 @@ def test_find_command_folder_in_path():
     found_path = find_command('foo', map(str, [path_one, path_two]))
     assert found_path == path_two/'foo'
 
+def test_does_not_find_command_because_there_is_no_path():
+    """
+    Test calling `pip.utils.find_command` when there is no PATH env variable
+    """
+    from pip.util import find_command
+    environ_before = os.environ
+    os.environ = {}
+    try:
+        find_command('anycommand')
+    except BadCommand:
+        e = sys.exc_info()[1]
+        assert e.args == ("Cannot find command 'anycommand'",)
+    else:
+        raise AssertionError("`find_command` should raise `BadCommand`")
+    finally:
+        os.environ = environ_before
+
 @patch('pip.util.get_pathext')
 @patch('os.path.isfile')
 def test_find_command_trys_all_pathext(mock_isfile, getpath_mock):