test_ast_parser_handles_exceptions fails on PyInstaller master & develop branches

[jayvdb]

test_ast_parser_handles_exceptions added in #227 depends on https://github.com/pyinstaller/pyinstaller/blob/6d4cce1f8eb80c0bf49d35876d28daa55a05800f/setup.py , and fails on master and develop branches of PyInstaller.

>       assert "altgraph" in result["install_requires"]
E       KeyError: 'install_requires'

c.f. https://github.com/pyinstaller/pyinstaller/blob/master/setup.py#L75

result for the current develop branch looks like {'setup_requires': ['setuptools >= 39.2.0'], 'cmdclass': {'build_bootloader': 'build_bootloader', 'build': 'MyBuild'}}

It is easy to update the test logic to work with an updated git submodule link, e.g. change the assert to

assert "setuptools >= 39.2.0" in result["setup_requires"]

but that may not exercise the intended code, and it is also brittle. An assert on cmdclass seems like it will be more stable.

If there was something specific about the old setup.py, that the new setup.py doesnt include , it would be good to extract out of the old pyinstaller a smaller testcase to prevent regressions.

Noting that #268 recommends removing the ast parsing used here. It might be helpful to copy the stripped down test case to be a PEP 517 test case.