hgmo: cast bytearray to bytes (bug 1506297); r=sheehan

Mercurial 4.8 may emit bytearray instances from its WSGI application.
This is apparently against PEP-3333 and mod_wsgi complains.

This commit works around the bug by filtering for bytearray in
WSGI application output and casting to bytes.

The upstream bug should be fixed in 4.8.1.

Differential Revision: https://phabricator.services.mozilla.com/D11539

--HG--
extra : moz-landing-system : lando

hgext/hgmo/__init__.py

@@ -100,6 +100,7 @@
     wireprotov1server,
 )
 from mercurial.hgweb import (
+    request as requestmod,
     webcommands,
     webutil,
 )
@@ -790,6 +791,14 @@ def mozbuildinfocommand(ui, repo, *paths, **opts):
     return
 
 
+def wsgisendresponse(orig, self):
+    for chunk in orig(self):
+        if isinstance(chunk, bytearray):
+            chunk = bytes(chunk)
+
+        yield chunk
+
+
 def pull(orig, repo, remote, *args, **kwargs):
     """Wraps exchange.pull to fetch the remote clonebundles.manifest."""
     res = orig(repo, remote, *args, **kwargs)
@@ -951,6 +960,10 @@ def hgwebfastannotate(orig, req, fctx, ui):
 
 
 def extsetup(ui):
+    # TRACKING hg49 4.8 would emit bytearray instances against PEP-3333.
+    extensions.wrapfunction(requestmod.wsgiresponse, 'sendresponse',
+                            wsgisendresponse)
+
     extensions.wrapfunction(exchange, 'pull', pull)
     extensions.wrapfunction(webutil, 'changesetentry', changesetentry)
     extensions.wrapfunction(webutil, 'changelistentry', changelistentry)