Bootstrap failures with Python 2

Three tests in ``test_ah_bootstrap.py`` are failing for me on Python 2.7:

```
______________________________________________________ test_bootstrap_from_archive _______________________________________________________

tmpdir = local('/private/var/folders/zy/t1l3sx310d3d6p0kyxqzlrnr0000gr/T/pytest-47/test_bootstrap_from_archive0')
testpackage = local('/private/var/folders/zy/t1l3sx310d3d6p0kyxqzlrnr0000gr/T/pytest-47/test_bootstrap_from_archive0/testpkg')
capsys = <_pytest.capture.CaptureFixture instance at 0x108a5b908>

    def test_bootstrap_from_archive(tmpdir, testpackage, capsys):
        """
        Tests importing _astropy_helpers_test_ from a .tar.gz source archive
        shipped alongside the package that uses it.
        """
    
        orig_repo = tmpdir.mkdir('orig')
    
        # Ensure ah_bootstrap is imported from the local directory
        import ah_bootstrap
    
        # Make a source distribution of the test package
        with silence():
            run_setup(str(testpackage.join('setup.py')),
                      ['sdist', '--dist-dir=dist', '--formats=gztar'])
    
        dist_dir = testpackage.join('dist')
        for dist_file in dist_dir.visit('*.tar.gz'):
            dist_file.copy(orig_repo)
    
        with orig_repo.as_cwd():
            # Write a test setup.py that uses ah_bootstrap; it also ensures that
            # any previous reference to astropy_helpers is first wiped from
            # sys.modules
            args = 'path={0!r}'.format(os.path.basename(str(dist_file)))
            orig_repo.join('setup.py').write(TEST_SETUP_PY.format(args=args))
    
            run_setup('setup.py', [])
    
            stdout, stderr = capsys.readouterr()
            path = stdout.splitlines()[-1].strip()
    
            # Installation from the .tar.gz should have resulted in a .egg
            # directory that the _astropy_helpers_test_ package was imported from
            eggs = glob.glob('*.egg')
>           assert eggs
E           assert []

astropy_helpers/tests/test_ah_bootstrap.py:242: AssertionError
________________________________________________________ test_download_if_needed _________________________________________________________

tmpdir = local('/private/var/folders/zy/t1l3sx310d3d6p0kyxqzlrnr0000gr/T/pytest-47/test_download_if_needed0')
testpackage = local('/private/var/folders/zy/t1l3sx310d3d6p0kyxqzlrnr0000gr/T/pytest-47/test_download_if_needed0/testpkg')
capsys = <_pytest.capture.CaptureFixture instance at 0x108b0f290>

    def test_download_if_needed(tmpdir, testpackage, capsys):
        """
        Tests the case where astropy_helpers was not actually included in a
        package, or is otherwise missing, and we need to "download" it.
    
        This does not test actually downloading from the internet--this is normally
        done through setuptools' easy_install command which can also install from a
        source archive.  From the point of view of ah_boostrap the two actions are
        equivalent, so we can just as easily simulate this by providing a setup.cfg
        giving the path to a source archive to "download" (as though it were a
        URL).
        """
    
        source = tmpdir.mkdir('source')
    
        # Ensure ah_bootstrap is imported from the local directory
        import ah_bootstrap
    
        # Make a source distribution of the test package
        with silence():
            run_setup(str(testpackage.join('setup.py')),
                      ['sdist', '--dist-dir=dist', '--formats=gztar'])
    
        dist_dir = testpackage.join('dist')
    
        with source.as_cwd():
            source.join('setup.py').write(TEST_SETUP_PY.format(
                args='download_if_needed=True'))
            source.join('setup.cfg').write(textwrap.dedent("""\
                [easy_install]
                find_links = {find_links}
            """.format(find_links=str(dist_dir))))
    
            run_setup('setup.py', [])
    
            stdout, stderr = capsys.readouterr()
    
            # Just take the last line--on Python 2.6 distutils logs warning
            # messages to stdout instead of stderr, causing them to be mixed up
            # with our expected output
            path = stdout.splitlines()[-1].strip()
    
            # easy_install should have worked by 'installing' astropy_helpers as a
            # .egg in the current directory
            eggs = glob.glob('*.egg')
>           assert eggs
E           assert []

astropy_helpers/tests/test_ah_bootstrap.py:298: AssertionError
______________________________________________________________ test_upgrade ______________________________________________________________

tmpdir = local('/private/var/folders/zy/t1l3sx310d3d6p0kyxqzlrnr0000gr/T/pytest-47/test_upgrade0')
capsys = <_pytest.capture.CaptureFixture instance at 0x108b5eef0>

    def test_upgrade(tmpdir, capsys):
        # Run the testpackage fixture manually, since we use it multiple times in
        # this test to make different versions of _astropy_helpers_test_
        orig_dir = testpackage(tmpdir.mkdir('orig'))
    
        # Make a test package that uses _astropy_helpers_test_
        source = tmpdir.mkdir('source')
        dist_dir = source.mkdir('dists')
        orig_dir.copy(source.join('_astropy_helpers_test_'))
    
        with source.as_cwd():
            setup_py = TEST_SETUP_PY.format(args='auto_upgrade=True')
            source.join('setup.py').write(setup_py)
    
            # This will be used to later to fake downloading the upgrade package
            source.join('setup.cfg').write(textwrap.dedent("""\
                [easy_install]
                find_links = {find_links}
            """.format(find_links=str(dist_dir))))
    
        # Make additional "upgrade" versions of the _astropy_helpers_test_
        # package--one of them is version 0.2 and the other is version 0.1.1.  The
        # auto-upgrade should ignore version 0.2 but use version 0.1.1.
        upgrade_dir_1 = testpackage(tmpdir.mkdir('upgrade_1'), version='0.2')
        upgrade_dir_2 = testpackage(tmpdir.mkdir('upgrade_2'), version='0.1.1')
    
        dists = []
        # For each upgrade package go ahead and build a source distribution of it
        # and copy that source distribution to a dist directory we'll use later to
        # simulate a 'download'
        for upgrade_dir in [upgrade_dir_1, upgrade_dir_2]:
            with silence():
                run_setup(str(upgrade_dir.join('setup.py')),
                          ['sdist', '--dist-dir=dist', '--formats=gztar'])
            dists.append(str(upgrade_dir.join('dist')))
            for dist_file in upgrade_dir.visit('*.tar.gz'):
                dist_file.copy(source.join('dists'))
    
        # Monkey with the PackageIndex in ah_bootstrap so that it is initialized
        # with the test upgrade packages, and so that it does not actually go out
        # to the internet to look for anything
        import ah_bootstrap
    
        class FakePackageIndex(PackageIndex):
            def __init__(self, *args, **kwargs):
                PackageIndex.__init__(self, *args, **kwargs)
                self.to_scan = dists
    
            def find_packages(self, requirement):
                # no-op
                pass
    
        ah_bootstrap.PackageIndex = FakePackageIndex
    
        try:
            with source.as_cwd():
                # Now run the source setup.py; this test is similar to
                # test_download_if_needed, but we explicitly check that the correct
                # *version* of _astropy_helpers_test_ was used
                run_setup('setup.py', [])
    
                stdout, stderr = capsys.readouterr()
                path = stdout.splitlines()[-1].strip()
                eggs = glob.glob('*.egg')
>               assert eggs
E               assert []

astropy_helpers/tests/test_ah_bootstrap.py:372: AssertionError
=================================================== 3 failed, 5 passed in 4.22 seconds ===================================================
```

@embray - do you see this too?
Nice ;)