Log Message:
py-dateutil: updated to 2.8.0

Version 2.8.0 (2019-02-04)

Data updates
- Updated tzdata version to to 2018i.

Features
- Added support for EXDATE parameters when parsing rrule strings.
- Added support for sub-minute time zone offsets in Python 3.6+.
- Switched the tzoffset, tzstr and gettz caches over to using weak
  references, so that the cache expires when no other references to the
  original tzinfo objects exist. This cache-expiry behavior is not
  guaranteed in the public interface and may change in the future. To improve
  performance in the case where transient references to the same time zones
  are repeatedly created but no strong reference is continuously held, a
  smaller "strong value" cache was also added.

Bugfixes
- Added time zone inference when initializing an rrule with a specified
  UNTIL but without an explicitly specified DTSTART; the time zone
  of the generated DTSTART will now be taken from the UNTIL rule.
- Fixed an issue where parser.parse would raise Decimal-specific errors
  instead of a standard ValueError if certain malformed values were parsed
  (e.g. NaN or infinite values).
- Fixed issue in parser where a tzinfos call explicitly returning
  None would throw a ValueError.
- Fixed incorrect parsing of certain dates earlier than 100 AD when repesented
  in the form "%B.%Y.%d", e.g. "December.0031.30".
- Add support for ISO 8601 times with comma as the decimal separator in the
  dateutil.parser.isoparse function.
- Changed handling of T24:00 to be compliant with the standard. T24:00
  now represents midnight on the *following* day.
- Fixed an issue where isoparser.parse_isotime was unable to handle the
  24:00 variant representation of midnight.
- Added support for more than 6 fractional digits in isoparse.
- Added 'z' (lower case Z) as valid UTC time zone in isoparser.
- Fixed a bug with base offset changes during DST in tzfile, and refactored
  the way base offset changes are detected.
- Fixed error condition in tz.gettz when a non-ASCII timezone is passed on
  Windows in Python 2.7.
- Improved performance and inspection properties of tzname methods.
- Removed unnecessary binary_type compatibility shims.
- Changed python setup.py test to print an error to stderr and exit
  with 1 instead of 0.
- Added a pyproject.toml file with build requirements and an explicitly
  specified build backend.

Documentation changes
- Added documentation for the rrule.rrulestr function.
- Added documentation for dateutil.tz.gettz.
- Add documentation for the dateutil.tz.win module and mocked out certain
  Windows-specific modules so that autodoc can still be run on non-Windows
  systems.
- Added changelog to documentation.
- Changed order of keywords in the rrule docstring.
- Improved documentation on the use of until and count parameters in
  rrule.
- Added an example of how to use a custom parserinfo subclass to parse
  non-standard datetime formats in the examples documentation for parser.
- Added doctest examples to tzfile documentation.
- Updated the documentation for relativedelta's weekday arguments.
- Improved explanation of the order that relativedelta components are
  applied in.
- Expanded the description and examples in the relativedelta class.
- Improved the contributing documentation to clarify where to put new changelog
  files.
- Fixed a broken doctest in the relativedelta module.
- Changed the default theme to sphinx_rtd_theme, and changed the sphinx
  configuration accordingly.
- Reorganized dateutil.tz documentation and fixed issue with the
  dateutil.tz docstring.
- Cleaned up malformed RST in the tz documentation.
- Corrected link syntax and updated URL to https for ISO year week number
  notation in relativedelta examples.