Only execute Python interpreters

[hroncok]

Fixes #535

This checks if the interpreter is anything with python or pypy in it.

Thus, avoiding executing e.g. php -m argcomplete._check_console_script ... (which succeeds).

[hroncok]

I can attempt to write a test for this, however, not today.

[kislyuk]

Thank you!

[hroncok]

I can attempt to write a test for this, however, not today.

I attempted to create a script with a shebang that passes even with the -m flag and succeeds.

#!/usr/bin/env echo

Such script can then be used like this:

    def test_foreign_scripts_not_broken(self):
        self.sh.run_command("cd " + TEST_DIR)
        self.sh.run_command("complete -W 'hello' echoer")
        self.sh.run_command(TestBashZshGlobalBase.install_cmd)
        self.assertTrue(self.sh.run_command("echoer h\t").endswith("echoer hello\r\n"))

However, I am not able to make it fail without the fix, so it is not useful as a test :/