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")
 
-withrw_repo.git.custom_environment(GIT_SSH=path):
-try:
-remote.fetch()
-exceptGitCommandErroraserr:
-assert'FOO'instr(err)
+# This only works if we are not evaluating git-push/pull output in a thread !
+importselect
+ifhasattr(select, 'poll'):
+withrw_repo.git.custom_environment(GIT_SSH=path):
+try:
+remote.fetch()
+exceptGitCommandErroraserr:
+assert'FOO'instr(err)
+# end
 # end
-# end
+# end if select.poll exists