Add comment explaining gitpython requirement

Also clean up some tabs.

Change-Id: If641a164c21dc7b13d48548558ea16e0c0a0b400
diff --git a/requirements.txt b/requirements.txt
index facc0ba..b718827 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,6 +7,10 @@
 Paste
 WebOb>=1.2.3
 paramiko>=1.8.0,<2.0.0
+# Using a local fork of gitpython until at least these changes are in a
+# release.
+# https://github.com/gitpython-developers/GitPython/pull/682
+# https://github.com/gitpython-developers/GitPython/pull/686
 -e git+https://github.com/jeblair/GitPython.git@zuul#egg=GitPython
 python-daemon>=2.0.4,<2.1.0
 extras