Install bazaar with --allow-external

tests/install.sh

@@ -3,7 +3,8 @@ pip install .
 pip install psutil
 if python -c 'import sys; sys.exit(1 * (sys.version_info[0] != 2))' ; then
 	# Python 2
-	pip install mercurial bzr
+	pip install mercurial
+	pip install --allow-external bzr bzr
 	if python -c 'import sys; sys.exit(1 * (sys.version_info[1] >= 7))' ; then
 		# Python 2.6
 		pip install unittest2 argparse