Weird deadlock (livelock?) in _posix.py when trying to run /usr/bin/env

[JarrettBillingsley]

I've run into this on two totally different versions of sublime text (3 and 4) on two totally different platforms (macOS and Linux) and I seem to be the only one who has so it must be something real weird about my configuration buuuuuuuuut

This line hangs when I try to use an ST package which uses shellenv, such as Rust Enhanced:

https://github.com/codexns/shellenv/blob/master/all/shellenv/_posix.py#L61

The bash process itself hangs, consuming 100% CPU of one core, but not doing any I/O.

I have no idea why this happens, but my workaround was to modify _posix.py to use bash's -c flag instead of writing the command to its standard input:

        if shell_name == 'bash':
            args.append('-i')
            args.append('-c')           # <----------- added
            args.append('/usr/bin/env') # <----------- added

        env_proc = subprocess.Popen(
            args,
            stdin=subprocess.PIPE,
            stdout=subprocess.PIPE,
            stderr=subprocess.STDOUT
        )

        if shell_name == 'bash':                                # <------- changed
            stdout, _ = env_proc.communicate()                  # <------- changed
        else:                                                   # <------- changed
            stdout, _ = env_proc.communicate(b'/usr/bin/env\n') # <------- changed

it now works flawlessly.