>>> import validators
>>> validators.domain('foo.com')
True
>>> validators.domain('foo.com.')
ValidationFailure(func=domain, args={'value': 'foo.com.'})
>>>

Reference: https://tools.ietf.org/html/rfc1034

When a user needs to type a domain name, the length of each label is
omitted and the labels are separated by dots ("."). Since a complete
domain name ends with the root label, this leads to a printed form which
ends in a dot. We use this property to distinguish between:

• a character string which represents a complete domain name
  (often called "absolute"). For example, "poneria.ISI.EDU."

• a character string that represents the starting labels of a
  domain name which is incomplete, and should be completed by
  local software using knowledge of the local domain (often
  called "relative"). For example, "poneria" used in the
  ISI.EDU domain.

Discussion: http://www.dns-sd.org/trailingdotsindomainnames.html