Merge branch 'ld/p4-cleanup-processes'

p4 updates. * ld/p4-cleanup-processes: git-p4: avoid leak of file handle when cloning git-p4: check for access to remote host earlier git-p4: cleanup better on error exit git-p4: create helper function importRevisions() git-p4: disable some pylint warnings, to get pylint output to something manageable git-p4: add P4CommandException to report errors talking to Perforce git-p4: make closeStreams() idempotent