Better parsing of changelog version entries

[Andreas Hasenack]

I got this crash when running the linter against https://code.launchpad.net/~paelzer/ubuntu/+source/libvirt/+git/libvirt/+ref/bug-1571209-sockfile-check-too-agressive:

$ git ubuntu lint
09/12/2017 14:54:29 - WARNING:Detached HEAD, assuming no namespace for tags. Pass --lint-namespace if this is incorrect.
E: must add exactly one changelog entry
Traceback (most recent call last):
  File "/snap/git-ubuntu/231/bin/git-ubuntu", line 22, in <module>
    main()
  File "/snap/git-ubuntu/231/gitubuntu/__main__.py", line 213, in main
    args.func(args)
  File "/snap/git-ubuntu/231/gitubuntu/lint.py", line 733, in main
    lint_pass = self.do_change_lint(commitish_string)
  File "/snap/git-ubuntu/231/gitubuntu/lint.py", line 637, in do_change_lint
    self.pkgname,
  File "/snap/git-ubuntu/231/gitubuntu/versioning.py", line 239, in next_sru_version_string
    afters
  File "/snap/git-ubuntu/231/gitubuntu/versioning.py", line 201, in _next_sru_version
    afters
  File "/snap/git-ubuntu/231/gitubuntu/versioning.py", line 129, in _bump_version_object
    new_version_suffix = bump_function(old_version_object, old_version_suffix)
  File "/snap/git-ubuntu/231/gitubuntu/versioning.py", line 163, in _bump_sru_version_suffix_string
    old_suffix_comps = _decompose_version_string(version_suffix_string)
  File "/snap/git-ubuntu/231/gitubuntu/versioning.py", line 100, in _decompose_version_string
    (version_string, ubuntu_series)
ValueError: Not sure how to decompose 0ubuntu13.1.22: series 1 not in expected format

d/changelog:
libvirt (1.2.2-0ubuntu13.1.22) trusty; urgency=medium

  * fix guest channel support (LP: #1393842).
    - d/p/virt-aa-helper-add-trusty-guest-agent-rule.patch: add apparmor rule
      for channels within guest namespace.
    - d/libvirt-bin.postinst: create channel directories if needed.

 -- Christian Ehrhardt <email address hidden> Mon, 28 Aug 2017 12:14:08 +0200