IOError if MANIFEST.in is missing

[mgedmin]

1. Get a git repo that has a MANIFEST.in, e.g. check-manifest's own repo
2. rm MANIFEST.in (but don't git rm)
3. Run check-manifest

I get

listing source files under version control: 11 files and directories
building an sdist: check-manifest-0.22.dev0.tar.gz: 10 files and directories
copying source files to a temporary directoryTraceback (most recent call last):
  File "/home/mg/.venv/bin/check-manifest", line 11, in <module>
    sys.exit(main())
  File "/home/mg/.venv/local/lib/python2.7/site-packages/check_manifest.py", line 685, in main
    update=args.update, python=args.python):
  File "/home/mg/.venv/local/lib/python2.7/site-packages/check_manifest.py", line 598, in check_manifest
    copy_files(source_files, tempsourcedir)
  File "/home/mg/.venv/local/lib/python2.7/site-packages/check_manifest.py", line 184, in copy_files
    shutil.copy2(filename, destfile)
  File "/usr/lib/python2.7/shutil.py", line 130, in copy2
    copyfile(src, dst)
  File "/usr/lib/python2.7/shutil.py", line 82, in copyfile
    with open(src, 'rb') as fsrc:
IOError: [Errno 2] No such file or directory: u'MANIFEST.in'