v13.0 Branch Preparation

Pins version of Flake8
Updates requirements to point to branch

Change-Id: I8b62a76fd1b06ad6b5a3fb13c321b3b15d7c1a16
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>
diff --git a/requirements-dev.in b/requirements-dev.in
index dc09a5e..ae6bd6a 100644
--- a/requirements-dev.in
+++ b/requirements-dev.in
@@ -14,7 +14,7 @@
 # limitations under the License.
 
 git+https://osm.etsi.org/gerrit/osm/IM.git@master#egg=osm-im
--r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=master
+-r https://osm.etsi.org/gitweb/?p=osm/IM.git;a=blob_plain;f=requirements.txt;hb=v13.0
 
 git+https://osm.etsi.org/gerrit/osm/osmclient.git@master#egg=osm-osmclient
--r https://osm.etsi.org/gitweb/?p=osm/osmclient.git;a=blob_plain;f=requirements.txt;hb=master
+-r https://osm.etsi.org/gitweb/?p=osm/osmclient.git;a=blob_plain;f=requirements.txt;hb=v13.0