py3: force bytestr conversion of "reason" in scmutil.callcatch() For instance, reason may be an InvalidURL as shown in added test.

tests-pure: fixing test-parseindex2 This is a followup to D7603 (49fa0b31ee1d) which broke the tests for pure Python implementation. There are two divergences between pure and C implementations: - the pure implementation would accept only -1 as slice end, whereas C accepts both -1 and len(index) - in pure Python, `headrevs` is provided by revlog.py, not by the index. Differential Revision: https://phab.mercurial-scm.org/D7707

rust-index: add a function to convert PyObject index for hg-core Function in hg-core need something implementing the `Graph` trait. Right now, the `hg-cpython` entry points directly turn the PyObject passed as argument into a `cindex::Index`. However, if we start having the option to use an Index in Rust, we need to dispatch between the different possible PyObject we could receive. So move the "duplicate" call into a unified function. When time come. It will be easy to update the logic of all interface when the time come. Differential Revision: https://phab.mercurial-scm.org/D7653