[Bug 1548972] Re: strcred.py is missing from packaging on Twisted 16/Xenial

[Mike Pontillo]

I'm not certain about Twisted, but what I can tell you is:

(1) Looking at Twisted 15.5.0, this module exists (and has roughly as much usage according to my grep)
(2) Well, we didn't see that traceback with the previous version of Twisted that was in Xenial (15.5)
(2a) ... but then again, MAAS doesn't directly use that module either; it seems the error surfaces when Twisted includes the cred_sshkeys plugin.

So either:
 - strcred module also didn't exist in the previous version of the python3 package, BUT Twisted never tried to load a plugin that depends on it
    OR
 - the strcred module existed in the previous version of python3-twisted, which is why we didn't notice this.

Either way, I think it's a regression.

I can reproduce it outside of MAAS by typing "twistd3" on the command
line and then scrolling up.

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Title:
  strcred.py is missing from packaging on Twisted 16/Xenial

Status in twisted package in Ubuntu:
  New

Bug description:
  While developing MAAS, I noticed the following traceback:

  Traceback (most recent call last):
    File "/usr/lib/python3/dist-packages/twisted/application/app.py", line 579, in parseOptions
      usage.Options.parseOptions(self, options)
    File "/usr/lib/python3/dist-packages/twisted/python/usage.py", line 262, in parseOptions
      for (cmd, short, parser, doc) in self.subCommands:
    File "/usr/lib/python3/dist-packages/twisted/application/app.py", line 596, in subCommands
      for plug in sorted(plugins, key=attrgetter('tapname')):
    File "/usr/lib/python3/dist-packages/twisted/plugin.py", line 213, in getPlugins
      allDropins = getCache(package)
  --- <exception caught here> ---
    File "/usr/lib/python3/dist-packages/twisted/plugin.py", line 171, in getCache
      provider = pluginModule.load()
    File "/usr/lib/python3/dist-packages/twisted/python/modules.py", line 389, in load
      return self.pathEntry.pythonPath.moduleLoader(self.name)
    File "/usr/lib/python3/dist-packages/twisted/python/reflect.py", line 303, in namedAny
      topLevelPackage = _importAndCheckStack(trialname)
    File "/usr/lib/python3/dist-packages/twisted/python/reflect.py", line 250, in _importAndCheckStack
      reraise(excValue, excTraceback)
    File "/usr/lib/python3/dist-packages/twisted/python/compat.py", line 412, in reraise
      raise exception.with_traceback(traceback)
    File "/usr/lib/python3/dist-packages/twisted/plugins/cred_sshkeys.py", line 15, in <module>
      from twisted.cred.strcred import ICheckerFactory
  builtins.ImportError: No module named 'twisted.cred.strcred'

  It looks like this file exists in the upstream distribution, but not
  in the .deb:

  $ dpkg -L python3-twisted | grep strcred
  /usr/lib/python3/dist-packages/twisted/cred/test/test_strcred.py

  $ apt-get source python3-twisted
  $ cd twisted-16.0.0~pre1
  $ find . | grep strcred
  ./twisted/cred/strcred.py
  ./twisted/cred/test/test_strcred.py

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: python3-twisted 16.0.0~pre1-1
  ProcVersionSignature: Ubuntu 4.4.0-4.19-generic 4.4.1
  Uname: Linux 4.4.0-4-generic x86_64
  ApportVersion: 2.20-0ubuntu3
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Tue Feb 23 11:51:23 2016
  PackageArchitecture: all
  SourcePackage: twisted
  UpgradeStatus: No upgrade log present (probably fresh install)

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