fix(test_git): handle select.poll() missing

In that case, the handler for processing stdout and stderr of the git
process is offloaded to threads. These currently don't return
any exception they raise.

We could easily fix this using an approach as shown
[here](http://goo.gl/hnVax6).

Author: Byron

git/test/test_git.py

@@ -192,10 +192,14 @@ def test_environment(self, rw_dir):
         rw_repo = Repo.init(os.path.join(rw_dir, 'repo'))
         remote = rw_repo.create_remote('ssh-origin', "ssh://git@server/foo")
 
-        with rw_repo.git.custom_environment(GIT_SSH=path):
-            try:
-                remote.fetch()
-            except GitCommandError as err:
-                assert 'FOO' in str(err)
+        # This only works if we are not evaluating git-push/pull output in a thread !
+        import select
+        if hasattr(select, 'poll'):
+            with rw_repo.git.custom_environment(GIT_SSH=path):
+                try:
+                    remote.fetch()
+                except GitCommandError as err:
+                    assert 'FOO' in str(err)
+                # end
             # end
-        # end
+        # end if select.poll exists