[SE-660] Tag editor on pathway edit page (#30)

* Pin mysqlclient to 1.3.14 PyMySQL/mysqlclient#306

Author: SSPJ

requirements/base.txt

@@ -12,6 +12,6 @@ git+https://github.com/alanjds/drf-nested-routers.git
 edx-auth-backends
 elasticsearch>=6.0.0,<7.0.0
 elasticsearch-dsl>=6.0.0,<7.0.0
-mysqlclient
+mysqlclient==1.3.14
 pytz
 sqlparse