utility: move MultipleSuccessorsError from __init__.py
The MultipleSuccessorsError is required in multiple modules in upcoming patches,
so let's move it to utility first.
#require test-repo
Enable obsolescence to avoid the warning issue when obsmarker are found
$ cat << EOF >> $HGRCPATH
> [diff]
> git = yes
> [experimental]
> evolution=all
> EOF
Go back in the hg repo
$ cd $TESTDIR/..
$ for node in `hg log --rev 'not public() and ::. and not desc("# no-check-commit")' --template '{node|short}\n'`; do
> hg export $node | ${RUNTESTDIR}/../contrib/check-commit > ${TESTTMP}/check-commit.out
> if [ $? -ne 0 ]; then
> echo "Revision $node does not comply with rules"
> echo '------------------------------------------------------'
> cat ${TESTTMP}/check-commit.out
> echo
> fi
> done