feat(launcher): output stderr for failing launchers

[twolfson]

In twolfson/karma-electron#17, twolfson/karma-electron#22, and personal experience, there's been scenarios when we're setting up Karma in CI and it's erroring out with no useful feedback. Typically this is due to a system dependency (e.g. missed an apt-get step).

This PR aims to resolve that by adding stderr to the output of failing launchers. In this PR:

• Added stderr output to launcher errorOutput
  • We didn't know if we wanted to be clever and indent everything so we went the simple route for now

Before:

30 03 2017 04:00:46.897:INFO [karma]: Karma v1.5.0 server started at http://0.0.0.0:9876/
30 03 2017 04:00:46.899:INFO [launcher]: Launching browser Firefox with unlimited concurrency
30 03 2017 04:00:46.906:INFO [launcher]: Starting browser Firefox
30 03 2017 04:00:46.922:ERROR [launcher]: Cannot start Firefox
	
30 03 2017 04:00:46.929:INFO [launcher]: Trying to start Firefox again (1/2).
30 03 2017 04:00:46.936:ERROR [launcher]: Cannot start Firefox
	
30 03 2017 04:00:46.940:INFO [launcher]: Trying to start Firefox again (2/2).
30 03 2017 04:00:46.949:ERROR [launcher]: Cannot start Firefox
	
30 03 2017 04:00:46.952:ERROR [launcher]: Firefox failed 2 times (cannot start). Giving up.
npm ERR! Test failed.  See above for more details.

After:

> gist-karma-launcher-fail@1.0.0 test /docker
> FIREFOX_BIN=$PWD/vendor/firefox/firefox karma start

30 03 2017 04:27:58.879:INFO [karma]: Karma v1.5.0 server started at http://0.0.0.0:9876/
30 03 2017 04:27:58.881:INFO [launcher]: Launching browser Firefox with unlimited concurrency
30 03 2017 04:27:58.888:INFO [launcher]: Starting browser Firefox
30 03 2017 04:27:58.925:ERROR [launcher]: Cannot start Firefox
	XPCOMGlueLoad error for file /docker/vendor/firefox/libmozgtk.so:
libgtk-3.so.0: cannot open shared object file: No such file or directory
Couldn't load XPCOM.

30 03 2017 04:27:58.930:INFO [launcher]: Trying to start Firefox again (1/2).
30 03 2017 04:27:58.941:ERROR [launcher]: Cannot start Firefox
	XPCOMGlueLoad error for file /docker/vendor/firefox/libmozgtk.so:
libgtk-3.so.0: cannot open shared object file: No such file or directory
Couldn't load XPCOM.

30 03 2017 04:27:58.943:INFO [launcher]: Trying to start Firefox again (2/2).
30 03 2017 04:27:58.959:ERROR [launcher]: Cannot start Firefox
	XPCOMGlueLoad error for file /docker/vendor/firefox/libmozgtk.so:
libgtk-3.so.0: cannot open shared object file: No such file or directory
Couldn't load XPCOM.

30 03 2017 04:27:58.964:ERROR [launcher]: Firefox failed 2 times (cannot start). Giving up.
npm ERR! Test failed.  See above for more details.

Here's a relevant gist to explore this for yourself:

https://gist.github.com/twolfson/f099e18cf5eb9cc55384e7a0582fbe10

twolfson/karma-electron#22 (comment)

[dignifiedquire]

Nice, I have seen a few bug reports where this was an issue. Could you add an e2e test with a fake launcher that prints something to stderr so we have a test of making sure this works as expected?

[twolfson]

Sure thing. After some browsing, it looks like karma-script-launcher and test/e2e/timeout are a great starting point. It's a good thing e2e only runs in Linux, otherwise we'd have .cmd/.bat issues to worry about in Windows x_x

[twolfson]

Alright, I've added the test in e2e 👍

[dignifiedquire]

Thank you