Normally when we pass to the start function parameters as for example '-parallel-runs', the function add_args append it to the string $call. Before execute the call the stderr to stdout redirection is appended to the string ( see line 121 in Local.php ).
If some custom parameters are passed to the start method, the value of the last custom parameter is sticked with the string "2>&1" in $call variable and this cause an exception.
Adding a space avoid this exception in this case.
Normally when we pass to the start function parameters as for example '-parallel-runs', the function add_args append it to the string $call. Before execute the call the stderr to stdout redirection is appended to the string ( see line 121 in Local.php ). If some custom parameters are passed to the start method, the value of the last custom parameter is sticked with the string "2>&1" in $call variable and this cause an exception. Adding a space avoid this exception in this case.