Pass cmd as list, not string, to subprocess.Popen. Otherwise, packages installed from files will fail with: OSError: [Errno 2] No such file or directory
modified to a list according to Pedro Algarvio's request
modified to a list according to Pedro Algarvio's request - fix bad brackets
Merge pull request #8014 from mihait/fix_pkg_from_file

Pass cmd as list, not string, to subprocess.Popen.