Update python-dateutil to 2.6.0

[safety-cli]

There's a new version of python-dateutil available.
You are currently using 2.5.3. I have updated it to 2.6.0

These links might come in handy: PyPI | Changelog | Docs

Changelog

2.6.0

---

• Added PEP-495-compatible methods to address ambiguous and imaginary dates in
  time zones in a backwards-compatible way. Ambiguous dates and times can now
  be safely represented by all dateutil time zones. Many thanks to Alexander
  Belopolski (abalkin) and Tim Peters tim-one for their inputs on how to
  address this. Original issues reported by Yupeng and zed (lP: 1390262,
  gh issues 57, 112, 249, 284, 286, prs 127, 225, 248, 264, 302).
• Added new methods for working with ambiguous and imaginary dates to the tz
  module. datetime_ambiguous() determines if a datetime is ambiguous for a given
  zone and datetime_exists() determines if a datetime exists in a given zone.
  This works for all fold-aware datetimes, not just those provided by dateutil.
  (gh issue 253, gh pr 302)
• Fixed an issue where dst() in Portugal in 1996 was returning the wrong value
  in tz.tzfile objects. Reported by abalkin (gh issue 128, pr 225)
• Fixed an issue where zoneinfo.ZoneInfoFile errors were not being properly
  deep-copied. (gh issue 226, pr 225)
• Refactored tzwin and tzrange as a subclass of a common class, tzrangebase, as
  there was substantial overlapping functionality. As part of this change,
  tzrange and tzstr now expose a transitions() function, which returns the
  DST on and off transitions for a given year. (gh issue 260, pr 302)
• Deprecated zoneinfo.gettz() due to confusion with tz.gettz(), in favor of
  get() method of zoneinfo.ZoneInfoFile objects. (gh issue 11, pr 310)
• For non-character, non-stream arguments, parser.parse now raises TypeError
  instead of AttributeError. (gh issues 171, 269, pr 247)
• Fixed an issue where tzfile objects were not properly handling dst() and
  tzname() when attached to datetime.time objects. Reported by ovacephaloid.
  (gh issue 292, pr 309)
• /usr/share/lib/zoneinfo was added to TZPATHS for compatibility with Solaris
  systems. Reported by dhduvall (gh issue 276, pr 307)
• tzoffset and tzrange objects now accept either a number of seconds or a
  datetime.timedelta() object wherever previously only a number of seconds was
  allowed. (gh pr 264, 277)
• datetime.timedelta objects can now be added to relativedelta objects. Reported
  and added by Alec Nikolas Reiter (justanr) (gh issue 282, pr 283
• Refactored relativedelta.weekday and rrule.weekday into a common base class
  to reduce code duplication. (gh issue 140, pr 311)
• An issue where the WKST parameter was improperly rendering in str(rrule) was
  reported and fixed by Daniel LePage (dplepage). (gh issue 262, pr 263)
• A replace() method has been added to rrule objects by jendas1, which creates
  new rrule with modified attributes, analogous to datetime.replace (gh pr 167)
• Made some significant performance improvements to rrule objects in Python 2.x
  (gh pr 245)
• All classes defining equality functions now return NotImplemented when
  compared to unsupported classes, rather than raising TypeError, to allow other
  classes to provide fallback support. (gh pr 236)
• Several classes have been marked as explicitly unhashable to maintain
  identical behavior between Python 2 and 3. Submitted by Roy Williams
  (rowillia) (gh pr 296)
• Trailing whitespace in easter.py has been removed. Submitted by OmgImAlexis
  (gh pr 299)
• Windows-only batch files in build scripts had line endings switched to CRLF.
  (gh pr 237)
• adamchainz updated the documentation links to reflect that the canonical
  location for readthedocs links is now at .io, not .org. (gh pr 272)
• Made some changes to the CI and codecov to test against newer versions of
  Python and pypy, and to adjust the code coverage requirements. For the moment,
  full pypy3 compatibility is not supported until a new release is available,
  due to upstream bugs in the old version affecting PEP-495 support.
  (gh prs 265, 266, 304, 308)
• The full PGP signing key fingerprint was added to the README.md in favor of
  the previously used long-id. Reported by valholl (gh issue 287, pr 304)
• Updated zoneinfo to 2016i. (gh issue 298, gh pr 306)

Got merge conflicts? Close this PR and delete the branch. I'll create a new PR for you.

Happy merging! 🤖