Display error messages from click

It turns out that django-click doesn't handle exceptions in the way we'd
expect. As a stop-gap, print them as `click` would

manage.py

@@ -2,14 +2,20 @@
 import os
 import sys
 
+from click import ClickException
+
 
 def main(argv):
     os.environ.setdefault("DJANGO_SETTINGS_MODULE",
                           "regparser.web.settings.dev")
 
     from django.core.management import execute_from_command_line
 
-    execute_from_command_line(argv)
+    try:
+        execute_from_command_line(argv)
+    except ClickException as e:
+        e.show()
+        sys.exit(e.exit_code)
 
 
 if __name__ == "__main__":