Log Message:
py-dateutil: updated to 2.7.3

Version 2.7.3:

Data updates
- Update tzdata to 2018e.

Bugfixes
- Fixed an issue where decimal.Decimal would cast NaN or infinite value in a
  parser.parse, which will raise decimal.Decimal-specific errors.
- Fixed a ValueError being thrown if tzinfos call explicity returns None.
- Fixed incorrect parsing of certain dates earlier than 100 AD when repesented
  in the form "%B.%Y.%d", e.g. "December.0031.30".
- Fixed a bug where automatically generated DTSTART was naive even if a
  specified UNTIL had a time zone. Automatically generated DTSTART will now
  take on the timezone of an UNTIL date, if provided.