dockerrpm: always use current user and group
Using uid 1000 and gid 1000 works by default in some cases,
but 'id -u' and 'id -g' should work in all cases.
Differential Revision: https://phab.mercurial-scm.org/D11767
#require black test-repo
Black needs the real USERPROFILE in order to run on Windows
#if msys
$ USERPROFILE="$REALUSERPROFILE"
$ export USERPROFILE
#endif
$ cd $RUNTESTDIR/..
$ black --check --diff `hg files 'set:(**.py + grep("^#!.*python")) - mercurial/thirdparty/**'`