Fix xdg-open.

[jsirois]

Previously desktop applications failed to launch, falling back
to console programs if available.

[ci skip-rust]
[ci skip-build-wheels]

[jsirois]

Previously lynx was used on my machine and only after I answered a prompt about TERM:

$ ./pants test --use-coverage --open-coverage --coverage-py-report="['html']" src/python/pants/engine/process_test.py
...
Wrote html coverage report to `dist/coverage/python`
/bin/xdg-open: line 881: www-browser: command not found
/bin/xdg-open: line 881: links2: command not found
/bin/xdg-open: line 881: elinks: command not found
/bin/xdg-open: line 881: links: command not found


  Your Terminal type is unknown!

  Enter a terminal type: [vt100] xterm-256color

TERMINAL TYPE IS SET TO xterm-256color

Now chrome is opened, which is expected:

$ ./pants test --use-coverage --open-coverage --coverage-py-report="['html']" src/python/pants/engine/process_test.py 
...
Wrote html coverage report to `dist/coverage/python`
$ Opening in existing browser session.
[0913/161509.424932:ERROR:nacl_helper_linux.cc(308)] NaCl helper process running without a sandbox!
Most likely you need to configure your SUID sandbox correctly

[Eric-Arellano]

Instead you can set something like hermetic_env=False in the constructor iirc. It will use the parent Pants process env.

[jsirois]

Instead you can set something like hermetic_env=False in the constructor iirc. It will use the parent Pants process env.

Ah, missed that. Done.

Hrm. That's clunky. At some point we'll install audit hooks to deny os.environ though I guess since you can mutate it in python.

[coveralls]

Coverage remained the same at 0.0% when pulling ea19c80 on jsirois:xdg-open/fix into 391d468 on pantsbuild:master.