Fix possible deadlock in install. When using`stderr=subprocess.PIPE, stdout=subprocess.PIPE`, you can (will) deadlock if one pipe fills up (in this case, stdout) while the other is being written too. The subprocess documentation is littered with warnings about this but somehow this has survived here for nearly 10 years. :) commit e3bed6a7172a03c2f03bc1355634ad7e9994b260