v13.0 Branch Preparation

Pins version of Flake8
Updates requirements to point to branch

Change-Id: I2e2a79cf8ef8ed211b74cb5baef6ef5c8c79f22d
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>
diff --git a/requirements-dev.in b/requirements-dev.in
index 733a1b3..e39d08c 100644
--- a/requirements-dev.in
+++ b/requirements-dev.in
@@ -14,7 +14,7 @@
 # limitations under the License.
 
 -e git+https://osm.etsi.org/gerrit/osm/common.git@master#egg=osm-common
--r https://osm.etsi.org/gitweb/?p=osm/common.git;a=blob_plain;f=requirements.txt;hb=master
+-r https://osm.etsi.org/gitweb/?p=osm/common.git;a=blob_plain;f=requirements.txt;hb=v13.0
 
 -e git+https://osm.etsi.org/gerrit/osm/N2VC.git@master#egg=n2vc
--r https://osm.etsi.org/gitweb/?p=osm/N2VC.git;a=blob_plain;f=requirements.txt;hb=master
+-r https://osm.etsi.org/gitweb/?p=osm/N2VC.git;a=blob_plain;f=requirements.txt;hb=v13.0