Travis CI build failures in test/test-find-python.js

[cclauss]

As discussed at #1820 (comment)

• Node Version: master
• Platform: Travis CI (Linux)
• Compiler:
• Module: test

Verbose output (from npm or node-gyp):

In #1815 at https://travis-ci.com/nodejs/node-gyp/jobs/214789663#L4479-L4504

[cclauss]

https://bugs.python.org/issue18338

• python2 --version writes to stderr
• python3 --version writes to stdout

https://github.com/nodejs/node-gyp/blob/master/test/test-find-python.js#L16-L26
I thought that the following would do the trick but it broke even more tests.

-       t.strictEqual(stdout, '')
-       t.ok(/Python 2/.test(stderr))
+       t.ok(/Python 2/.test(stderr) || /Python 3/.test(stdout))