actions: Error out when the range for --around is missing

Previously this case was handled by the int() cast in the try/except
block but resulted in a confusing error message. Make clear to the user
what exactly went wrong.

1 files changed, 3 insertions, 0 deletions

diff --git a/quarg/actions.py b/quarg/actions.py
index e1fbc57..528d515 100644
--- a/quarg/actions.py
+++ b/quarg/actions.py
@@ -46,6 +46,9 @@ class ParseAround(argparse.Action):
     def __call__(self, parser, namespace, aroundspec, option_string=None):
         if '/' in aroundspec:
             datespec, rangespec = aroundspec.split('/', 1)
+            if not rangespec:
+                errx('Missing range for --around')
+
             try:
                 hour_range = int(rangespec)
             except ValueError as err: