py3: use util.forcebytestr instead of str for converting errors to bytes

Differential Revision: https://phab.mercurial-scm.org/D2269

hgext/transplant.py

@@ -311,7 +311,7 b' class transplanter(object):'
                 p1 = repo.dirstate.p1()
                 p2 = node
                 self.log(user, date, message, p1, p2, merge=merge)
-                self.ui.write(str(inst) + '\n')
+                self.ui.write(util.forcebytestr(inst) + '\n')
                 raise TransplantError(_('fix up the working directory and run '
                                         'hg transplant --continue'))
         else:

mercurial/patch.py

@@ -1459,7 +1459,7 b' class binhunk(object):'
                 dec.append(util.b85decode(line[1:])[:l])
             except ValueError as e:
                 raise PatchError(_('could not decode "%s" binary patch: %s')
-                                 % (self._fname, str(e)))
+                                 % (self._fname, util.forcebytestr(e)))
             line = getline(lr, self.hunk)
         text = zlib.decompress(''.join(dec))
         if len(text) != size: