check_version_conflict

# File lib/rubygems/specification.rb, line 2271
  def check_version_conflict other # :nodoc:
    return if self.version == other.version

    # This gem is already loaded.  If the currently loaded gem is not in the
    # list of candidate gems, then we have a version conflict.

    msg = "can't activate #{full_name}, already activated #{other.full_name}"

    e = Gem::LoadError.new msg
    e.name = self.name
    # TODO: e.requirement = dep.requirement

    raise e
  end