pure: use string for exception in the pure version of base85
Without this change, running the test with python3 and --pure gives the
following error::
--- /home/marmoute/src/mercurial-dev/tests/test-import-git.t
+++ /home/marmoute/src/mercurial-dev/tests/test-import-git.t.err
@@ -518,7 +518,7 @@
>
> EOF
applying patch from stdin
- abort: could not decode "binary2" binary patch: bad base85 character at position 6
+ abort: could not decode "binary2" binary patch: b'bad base85 character at position 6'
[255]
$ hg revert -aq
To make the cext implementation, we use a "native" string for the exception.
This fix the test failure.
[workspace]
members = ["hg-core", "hg-direct-ffi", "hg-cpython"]
exclude = ["chg", "hgcli"]