Test cyclic imports

    >>> from testsuite import create_tree

    >>> create_tree('''
    ... -- foo/__init__.py --
    ...
    ... -- foo/bar.py --
    ... from . import baz
    ... from . import qux
    ...
    ... -- foo/baz.py --
    ... from . import bar
    ... from . import mux
    ...
    ... -- foo/qux.py --
    ... -- foo/mux.py --
    ... ''')

    >>> from findimports import ModuleGraph
    >>> g = ModuleGraph()
    >>> g.parsePathname('foo')
    >>> g.printImports()
    foo.__init__:
    <BLANKLINE>
    foo.bar:
      foo.baz
      foo.qux
    foo.baz:
      foo.bar
      foo.mux
    foo.mux:
    <BLANKLINE>
    foo.qux:
    <BLANKLINE>

    >>> cg = g.collapseCycles()
    >>> cg.printImports()
    foo.__init__:
    <BLANKLINE>
    foo.bar
    foo.baz:
      foo.mux
      foo.qux
    foo.mux:
    <BLANKLINE>
    foo.qux:
    <BLANKLINE>

This is enabled when you pass --collapse to findimports:

    >>> from findimports import main
    >>> exitcode = main(['findimports', '-c'])
    foo.__init__:
    <BLANKLINE>
    foo.bar
    foo.baz:
      foo.mux
      foo.qux
    foo.mux:
    <BLANKLINE>
    foo.qux:
    <BLANKLINE>

