fix(test_cmd): handle GitCommandNotFound in test

Related to gitpython-developers#248

Author: Byron

git/test/test_git.py

@@ -19,6 +19,7 @@
 from git import (
     Git,
     GitCommandError,
+    GitCommandNotFound,
     Repo
 )
 from gitdb.test.lib import with_rw_directory
@@ -127,11 +128,7 @@ def test_version(self):
 
     def test_cmd_override(self):
         prev_cmd = self.git.GIT_PYTHON_GIT_EXECUTABLE
-        if os.name == 'nt':
-            exc = GitCommandError
-        else:
-            exc = OSError
-        # end handle windows case
+        exc = GitCommandNotFound
         try:
             # set it to something that doens't exist, assure it raises
             type(self.git).GIT_PYTHON_GIT_EXECUTABLE = os.path.join(