added packages to python requirements file

BUG=chromium:322308
TEST=run_all_test.py

Change-Id: I5a7c829b7266085da2c6760de51e771a599bebda
Reviewed-on: https://chromium-review.googlesource.com/177712
Reviewed-by: Byron Kubert <byronk@chromium.org>
Commit-Queue: Byron Kubert <byronk@chromium.org>
Tested-by: Byron Kubert <byronk@chromium.org>
diff --git a/requirements.txt b/requirements.txt
index 750e280..313292f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,6 @@
 pylint==1.0.0
-mock==1.0.1
 pep8==1.4.6
 epydoc==3.0.1
-
+sphinx=1.0
+mock==1.0.1
+pexpect==2.3