Fix non-padded month parsing for ISO-8601. Also added test.

Author: tasos-ukko

pendulum/parsing/iso8601.py

@@ -22,7 +22,7 @@
     "    (?P<classic>"  # Classic date (YYYY-MM-DD) or ordinal (YYYY-DDD)
     "        (?P<year>\d{4})"  # Year
     "        (?P<monthday>"
-    "            (?P<monthsep>-)?(?P<month>\d{2})"  # Month (optional)
+    "            (?P<monthsep>-)?(?P<month>\d{1,2})"  # Month (optional)
     "            ((?P<daysep>-)?(?P<day>\d{1,2}))?"  # Day (optional)
     "        )?"
     "    )"

tests/parsing/test_parse_iso8601.py

@@ -16,6 +16,10 @@ def test_parse_iso8601():
     assert date(2016, 10, 6) == parse_iso8601("2016-10-06")
     assert date(2016, 10, 6) == parse_iso8601("20161006")
 
+    # Month only, both padded and unpadded
+    assert date(2016, 7, 1) == parse_iso8601("2016-7")
+    assert date(2016, 7, 1) == parse_iso8601("2016-07")
+
     # Time
     assert time(20, 16, 10, 0) == parse_iso8601("201610")