registration.py: Don't catch exception that can't be thrown.

A previous commit changed a `get` (which can throw `DoesNotExist`) to use an
existing object, but kept the `try` / `except` block:

4bf3ace

Removing this unused code path allows us to achieve 100% test coverage.

zerver/views/registration.py

@@ -197,16 +197,10 @@ def accounts_register(request):
 
         # FIXME: sanitize email addresses and fullname
         if existing_user_profile is not None and existing_user_profile.is_mirror_dummy:
-            try:
-                user_profile = existing_user_profile
-                do_activate_user(user_profile)
-                do_change_password(user_profile, password)
-                do_change_full_name(user_profile, full_name)
-            except UserProfile.DoesNotExist:
-                user_profile = do_create_user(email, password, realm, full_name, short_name,
-                                              prereg_user=prereg_user,
-                                              tos_version=settings.TOS_VERSION,
-                                              newsletter_data={"IP": request.META['REMOTE_ADDR']})
+            user_profile = existing_user_profile
+            do_activate_user(user_profile)
+            do_change_password(user_profile, password)
+            do_change_full_name(user_profile, full_name)
         else:
             user_profile = do_create_user(email, password, realm, full_name, short_name,
                                           prereg_user=prereg_user,