py3: conditionalize test-lfs-serve-access.t for Python 3.8

This is another case where Python 3.8's traceback printing
varies subtly from older Python versions. Again, I'm not sure
why. But this is apparently the new behavior.

With this change, test-lfs-serve-access.t now passes on Python
3.8!

Differential Revision: https://phab.mercurial-scm.org/D7947

tests/test-lfs-serve-access.t

@@ -353,7 +353,8 b' Test a checksum failure during the proce'
   $LOCALIP - - [$ERRDATE$] HG error:  Traceback (most recent call last): (glob)
   $LOCALIP - - [$ERRDATE$] HG error:      localstore.download(oid, req.bodyfh, req.headers[b'Content-Length'])
   $LOCALIP - - [$ERRDATE$] HG error:      super(badstore, self).download(oid, src, contentlength)
-  $LOCALIP - - [$ERRDATE$] HG error:      _(b'corrupt remote lfs object: %s') % oid (glob)
+  $LOCALIP - - [$ERRDATE$] HG error:      raise LfsCorruptionError( (glob) (py38 !)
+  $LOCALIP - - [$ERRDATE$] HG error:      _(b'corrupt remote lfs object: %s') % oid (glob) (no-py38 !)
   $LOCALIP - - [$ERRDATE$] HG error:  LfsCorruptionError: corrupt remote lfs object: b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c (no-py3 !)
   $LOCALIP - - [$ERRDATE$] HG error:  hgext.lfs.blobstore.LfsCorruptionError: corrupt remote lfs object: b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c (py3 !)
   $LOCALIP - - [$ERRDATE$] HG error:   (glob)
@@ -363,9 +364,11 b' Test a checksum failure during the proce'
       self.do_hgweb()
       for chunk in self.server.application(env, self._start_response):
       for r in self._runwsgi(req, res, repo):
-      rctx, req, res, self.check_perm
+      handled = wireprotoserver.handlewsgirequest( (py38 !)
+      return _processbasictransfer( (py38 !)
+      rctx, req, res, self.check_perm (no-py38 !)
       return func(*(args + a), **kw) (no-py3 !)
-      rctx.repo, req, res, lambda perm: checkperm(rctx, req, perm)
+      rctx.repo, req, res, lambda perm: checkperm(rctx, req, perm) (no-py38 !)
       res.setbodybytes(localstore.read(oid))
       blob = self._read(self.vfs, oid, verify)
       raise IOError(errno.EIO, r'%s: I/O error' % oid.decode("utf-8"))
@@ -376,7 +379,8 b' Test a checksum failure during the proce'
   $LOCALIP - - [$ERRDATE$] HG error:      res.setbodybytes(localstore.read(oid)) (glob)
   $LOCALIP - - [$ERRDATE$] HG error:      blob = self._read(self.vfs, oid, verify) (glob)
   $LOCALIP - - [$ERRDATE$] HG error:      blobstore._verify(oid, b'dummy content') (glob)
-  $LOCALIP - - [$ERRDATE$] HG error:      hint=_(b'run hg verify'), (glob)
+  $LOCALIP - - [$ERRDATE$] HG error:      raise LfsCorruptionError( (glob) (py38 !)
+  $LOCALIP - - [$ERRDATE$] HG error:      hint=_(b'run hg verify'), (glob) (no-py38 !)
   $LOCALIP - - [$ERRDATE$] HG error:  LfsCorruptionError: detected corrupt lfs object: 276f73cfd75f9fb519810df5f5d96d6594ca2521abd86cbcd92122f7d51a1f3d (no-py3 !)
   $LOCALIP - - [$ERRDATE$] HG error:  hgext.lfs.blobstore.LfsCorruptionError: detected corrupt lfs object: 276f73cfd75f9fb519810df5f5d96d6594ca2521abd86cbcd92122f7d51a1f3d (py3 !)
   $LOCALIP - - [$ERRDATE$] HG error:   (glob)