setup.py: add -s/--sign option to release command

requires bump2version >= 0.5.7

setup.py

@@ -80,10 +80,12 @@ class release(bump_version):
 
  user_options = [
  ("message=", 'm', "message containing the release notes"),
+ ("sign", "s", "make a GPG-signed tag, using the default key"),
  ]
 
  def initialize_options(self):
  self.message = None
+ self.sign = False
 
  def finalize_options(self):
  import re
@@ -110,6 +112,7 @@ def finalize_options(self):
  raise DistutilsSetupError("release notes message is empty")
 
  self.message = u"v{new_version}\n\n%s" % message
+ self.sign = bool(self.sign)
 
  @staticmethod
  def edit_release_notes():
@@ -142,13 +145,14 @@ def run(self):
  self.bumpversion("release",
  tag=True,
  message="Release {new_version}",
- tag_message=self.message)
+ tag_message=self.message,
+ sign_tags=self.sign)
 
 
 needs_wheel = {'bdist_wheel'}.intersection(sys.argv)
 wheel = ['wheel'] if needs_wheel else []
 needs_bump2version = {'release', 'bump_version'}.intersection(sys.argv)
-bump2version = ['bump2version'] if needs_bump2version else []
+bump2version = ['bump2version >= 0.5.7'] if needs_bump2version else []
 
 with open('README.rst', 'r', encoding='utf-8') as f:
  long_description = f.read()