If a process filled up the buffer of the standard error pipe before closing the
standard output pipe, it would hang. As a result, the call to
stream_get_contents for the standard output pipe would not return, as the
standard error pipe needs to be read from in order for the process to continue.
This change uses stream_select to read from both pipes whenever data becomes
available.
Some tests compare the result to english strings.
Do not test UnixCommandExecutor on Windows.
PharTest: explain why PHAR writing test are skipped.
InstallCommandTest: mock checkRequirements to allow the tests to run.
Run php_parallel_lint before all other tests.
Close#846