pytest failures with python 3.8

[lucianposton]

Tests fail due to python 3.8 warnings that don't show up when byte code is already compiled.

Before running tests, clear out byte code and disable it for future test runs:

find . -name '*.pyc' -delete
export PYTHONDONTWRITEBYTECODE=1
pytest -vv

See test failures caused by 3.8 warnings e.g.:

________________________ TestCLI.test_exec_vint_with_unexistent_file _________________________

self = <test.acceptance.test_cli.TestCLI testMethod=test_exec_vint_with_unexistent_file>

    def test_exec_vint_with_unexistent_file(self):
        cmd = ['bin/vint', '/path/to/unexistent']

        with self.assertRaises(subprocess.CalledProcessError) as context_manager:
            subprocess.check_output(cmd,
                                    stderr=subprocess.STDOUT,
                                    universal_newlines=True)

        got_output = context_manager.exception.output

        expected_output_pattern = r'^vint ERROR:'
>       self.assertRegex(got_output, expected_output_pattern)

test/acceptance/test_cli.py:86: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
test/acceptance/test_cli.py:11: in assertRegex
    assertRegexpMatches(string, pattern)
E   AssertionError: Regex didn't match: '^vint ERROR:' not found in '/home/worch/vint/vint/ast/plugin/scope_plugin/scope_linker.py:389: SyntaxWarning: "is not" with a literal. Did you mean "!="?\n  is_declared_with_range = attr[\'range\'] is not 0\n/home/worch/vint/vint/ast/plugin/scope_plugin/scope_linker.py:395: SyntaxWarning: "is not" with a literal. Did you mean "!="?\n  is_declared_with_dict = attr[\'dict\'] is not 0 \\\nvint ERROR: no such file or directory: `/path/to/unexistent`\n'

[blueyed]

Thanks for the report. But I guess this is fixed in master (f8bae71), also available as v0.4a2.