diff --git a/Lib/packaging/database.py b/Lib/packaging/database.py
index e3c57ba..67946a2 100644
--- a/Lib/packaging/database.py
+++ b/Lib/packaging/database.py
@@ -72,7 +72,7 @@
     _cache_generated_egg = False
 
 
-def _yield_distributions(include_dist, include_egg, paths=sys.path):
+def _yield_distributions(include_dist, include_egg, paths):
     """
     Yield .dist-info and .egg(-info) distributions, based on the arguments
 
@@ -92,7 +92,7 @@
                 yield EggInfoDistribution(dist_path)
 
 
-def _generate_cache(use_egg_info=False, paths=sys.path):
+def _generate_cache(use_egg_info, paths):
     global _cache_generated, _cache_generated_egg
 
     if _cache_generated_egg or (_cache_generated and not use_egg_info):
@@ -472,7 +472,7 @@
     return '-'.join([name, normalized_version]) + file_extension
 
 
-def get_distributions(use_egg_info=False, paths=sys.path):
+def get_distributions(use_egg_info=False, paths=None):
     """
     Provides an iterator that looks for ``.dist-info`` directories in
     ``sys.path`` and returns :class:`Distribution` instances for each one of
@@ -482,6 +482,9 @@
     :rtype: iterator of :class:`Distribution` and :class:`EggInfoDistribution`
             instances
     """
+    if paths is None:
+        paths = sys.path
+
     if not _cache_enabled:
         for dist in _yield_distributions(True, use_egg_info, paths):
             yield dist
@@ -513,7 +516,7 @@
 
     :rtype: :class:`Distribution` or :class:`EggInfoDistribution` or None
     """
-    if paths == None:
+    if paths is None:
         paths = sys.path
 
     if not _cache_enabled:
@@ -632,7 +635,7 @@
 def get_file_path(distribution_name, relative_path):
     """Return the path to a resource file."""
     dist = get_distribution(distribution_name)
-    if dist != None:
+    if dist is not None:
         return dist.get_resource_path(relative_path)
     raise LookupError('no distribution named %r found' % distribution_name)
 
diff --git a/Lib/packaging/install.py b/Lib/packaging/install.py
index c5bda45..551ece1 100644
--- a/Lib/packaging/install.py
+++ b/Lib/packaging/install.py
@@ -54,10 +54,8 @@
         try:
             os.makedirs(os.path.dirname(new))
         except OSError as e:
-            if e.errno == errno.EEXIST:
-                pass
-            else:
-                raise e
+            if e.errno != errno.EEXIST:
+                raise
         os.rename(old, new)
         yield old, new
 
@@ -169,7 +167,7 @@
         os.chdir(old_dir)
 
 
-def install_dists(dists, path, paths=sys.path):
+def install_dists(dists, path, paths=None):
     """Install all distributions provided in dists, with the given prefix.
 
     If an error occurs while installing one of the distributions, uninstall all
@@ -196,13 +194,13 @@
             # reverting
             for installed_dist in installed_dists:
                 logger.info('Reverting %s', installed_dist)
-                _remove_dist(installed_dist, paths)
+                remove(installed_dist.name, paths)
             raise e
     return installed_dists
 
 
 def install_from_infos(install_path=None, install=[], remove=[], conflicts=[],
-                       paths=sys.path):
+                       paths=None):
     """Install and remove the given distributions.
 
     The function signature is made to be compatible with the one of get_infos.
@@ -383,11 +381,7 @@
             infos[key].extend(new_infos[key])
 
 
-def _remove_dist(dist, paths=sys.path):
-    remove(dist.name, paths)
-
-
-def remove(project_name, paths=sys.path, auto_confirm=True):
+def remove(project_name, paths=None, auto_confirm=True):
     """Removes a single project from the installation.
 
     Returns True on success
@@ -539,7 +533,6 @@
 
 def _main(**attrs):
     if 'script_args' not in attrs:
-        import sys
         attrs['requirements'] = sys.argv[1]
     get_infos(**attrs)
 
diff --git a/Lib/packaging/tests/test_command_build_ext.py b/Lib/packaging/tests/test_command_build_ext.py
index 9729559..d8936d4 100644
--- a/Lib/packaging/tests/test_command_build_ext.py
+++ b/Lib/packaging/tests/test_command_build_ext.py
@@ -29,7 +29,6 @@
         # Note that we're making changes to sys.path
         super(BuildExtTestCase, self).setUp()
         self.tmp_dir = self.mkdtemp()
-        self.sys_path = sys.path, sys.path[:]
         sys.path.append(self.tmp_dir)
         filename = _get_source_filename()
         if os.path.exists(filename):
@@ -107,8 +106,7 @@
     def tearDown(self):
         # Get everything back to normal
         unload('xx')
-        sys.path = self.sys_path[0]
-        sys.path[:] = self.sys_path[1]
+        sys.path.remove(self.tmp_dir)
         if sys.version > "2.6":
             site.USER_BASE = self.old_user_base
             build_ext.USER_BASE = self.old_user_base
diff --git a/Lib/packaging/tests/test_database.py b/Lib/packaging/tests/test_database.py
index e965c60..3eeda83 100644
--- a/Lib/packaging/tests/test_database.py
+++ b/Lib/packaging/tests/test_database.py
@@ -259,12 +259,11 @@
         disable_cache()
         # Setup the path environment with our fake distributions
         current_path = os.path.abspath(os.path.dirname(__file__))
-        self.sys_path = sys.path[:]
         self.fake_dists_path = os.path.join(current_path, 'fake_dists')
         sys.path.insert(0, self.fake_dists_path)
 
     def tearDown(self):
-        sys.path[:] = self.sys_path
+        sys.path.remove(self.fake_dists_path)
         enable_cache()
         super(TestDatabase, self).tearDown()
 
@@ -488,20 +487,20 @@
         dists = [('choxie', '2.0.0.9'), ('grammar', '1.0a4'),
                  ('towel-stuff', '0.1'), ('babar', '0.1')]
 
-        checkLists([], _yield_distributions(False, False))
+        checkLists([], _yield_distributions(False, False, sys.path))
 
         found = [(dist.name, dist.metadata['Version'])
-                 for dist in _yield_distributions(False, True)
+                 for dist in _yield_distributions(False, True, sys.path)
                  if dist.path.startswith(self.fake_dists_path)]
         checkLists(eggs, found)
 
         found = [(dist.name, dist.metadata['Version'])
-                 for dist in _yield_distributions(True, False)
+                 for dist in _yield_distributions(True, False, sys.path)
                  if dist.path.startswith(self.fake_dists_path)]
         checkLists(dists, found)
 
         found = [(dist.name, dist.metadata['Version'])
-                 for dist in _yield_distributions(True, True)
+                 for dist in _yield_distributions(True, True, sys.path)
                  if dist.path.startswith(self.fake_dists_path)]
         checkLists(dists + eggs, found)