[bugfix] SQL Lab 'MySQL has gone away' (apache#150)

* Cherry pick apache#4581

* Add flask-compress cherry

* Add shortner fix

* Add Return __time in Druid scan apache#4504

* Picking cherry Fixing regression from apache#4500 (apache#4549)

* [bugfix] SQL Lab 'MySQL has gone away'

It appears the 'MySQL has gone away' is triggered by the line of code
I wrapped in a try block here.

This is a temporary fix, there will be another PR shortly getting to the
bottom of this.

Related:
https://github.com/lyft/druidstream/issues/40

superset_config.py

@@ -173,7 +173,13 @@ class CeleryConfig(object):
 def get_user_email_cached(username, security_manager):
     """to avoid doing multiple round trips"""
     if username not in cached_user_emails:
-        user = security_manager.find_user(username=username)
+        user = None
+        try:
+            user = security_manager.find_user(username=username)
+        except Exception as e:
+            # Pessimistic to avoid 'MySQL has gone away'
+            logging.error("Couldn't fetch user info")
+            logging.exception(e)
         if user and user.email:
             cached_user_emails[username] = user.email
     return cached_user_emails.get(username)