pyflakes stacktrace: TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

[Scott Moser]

$ cat x/__init__.py
def greet(name):
    print("Hello, %s. Happy to see you." % name)

$ cat x/welcome.py
from . import greet

if __name__ == '__main__':
    import sys
    greet(sys.argv[1])

# python -m x.welcome Scott
Hello, Scott. Happy to see you.

# python3 -m x.welcome Scott
Hello, Scott. Happy to see you.

# python -m pyflakes x/
Traceback (most recent call last):
  File "/usr/lib/python2.7/runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/usr/lib/python2.7/dist-packages/pyflakes/__main__.py", line 5, in <module>
    main(prog='pyflakes')
  File "/usr/lib/python2.7/dist-packages/pyflakes/api.py", line 184, in main
    warnings = checkRecursive(args, reporter)
  File "/usr/lib/python2.7/dist-packages/pyflakes/api.py", line 141, in checkRecursive
    warnings += checkPath(sourcePath, reporter)
  File "/usr/lib/python2.7/dist-packages/pyflakes/api.py", line 108, in checkPath
    return check(codestr, filename, reporter)
  File "/usr/lib/python2.7/dist-packages/pyflakes/api.py", line 69, in check
    w = checker.Checker(tree, filename)
  File "/usr/lib/python2.7/dist-packages/pyflakes/checker.py", line 416, in __init__
    self.handleChildren(tree)
  File "/usr/lib/python2.7/dist-packages/pyflakes/checker.py", line 738, in handleChildren
    self.handleNode(node, tree)
  File "/usr/lib/python2.7/dist-packages/pyflakes/checker.py", line 785, in handleNode
    handler(node)
  File "/usr/lib/python2.7/dist-packages/pyflakes/checker.py", line 1164, in IMPORTFROM
    node.module, alias.name)
  File "/usr/lib/python2.7/dist-packages/pyflakes/checker.py", line 212, in __init__
    full_name = module + '.' + self.real_name
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: pyflakes 1.2.2-1
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
Date: Tue May 10 14:29:53 2016
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
SourcePackage: pyflakes
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.