extensions: gracefully warn when doing min version check with no local version
After doing a `make clean`, I started getting cryptic failures to import
extensions with the `minimumhgversion` attribute on py3:
*** failed to import extension evolve: '>' not supported between instances of 'int' and 'NoneType'
*** failed to import extension topic: '>' not supported between instances of 'int' and 'NoneType'
This now handles the `(None, None)` tuple before comparing, and disables the
extension with the same friendly message as in py2.
Differential Revision: https://phab.mercurial-scm.org/D9363
#require no-windows
#testcases safe normal
#if safe
$ echo "[format]" >> $HGRCPATH
$ echo "exp-share-safe = True" >> $HGRCPATH
#endif
$ . "$TESTDIR/remotefilelog-library.sh"
$ cat >> $HGRCPATH <<EOF
> [extensions]
> remotefilelog=
> share=
> EOF
$ hg init master
$ cd master
$ cat >> .hg/hgrc <<EOF
> [remotefilelog]
> server=True
> EOF
$ echo x > x
$ hg commit -qAm x
$ cd ..
$ hgcloneshallow ssh://user@dummy/master source --noupdate -q
$ hg share source dest
updating working directory
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg -R dest unshare