Merge branch 'release/1.0.1'1.0.1

1 files changed, 11 insertions, 4 deletions

diff --git a/pip/util.py b/pip/util.py
index d2dae97a8..b9c32525b 100644
--- a/pip/util.py
+++ b/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
@@ -71,12 +71,12 @@ 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
     if pathext is None:
-        pathext = os.environ.get('PATHEXT', '.COM;.EXE;.BAT;.CMD')
+        pathext = get_pathext()
     pathext = [ext for ext in pathext.lower().split(os.pathsep)]
     # don't use extensions if the command ends with one of them
     if os.path.splitext(cmd)[1].lower() in pathext:
@@ -92,9 +92,16 @@ 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"""
+    if default_pathext is None:
+        default_pathext = os.pathsep.join([ '.COM', '.EXE', '.BAT', '.CMD' ])
+    pathext = os.environ.get('PATHEXT', default_pathext)
+    return pathext
+
 def ask(message, options):
     """Ask the message interactively, with the given possible responses"""
     while 1: