[AIRFLOW-520] Fix Version Info in Flask UI (#4072)

Author: kaxil

airflow/www/views.py

@@ -37,7 +37,6 @@
 import markdown
 import nvd3
 import pendulum
-import pkg_resources
 import sqlalchemy as sqla
 from flask import (
     abort, jsonify, redirect, url_for, request, Markup, Response,
@@ -3052,7 +3051,7 @@ class VersionView(wwwutils.SuperUserMixin, BaseView):
     def version(self):
         # Look at the version from setup.py
         try:
-            airflow_version = pkg_resources.require("apache-airflow")[0].version
+            airflow_version = airflow.__version__
         except Exception as e:
             airflow_version = None
             logging.error(e)