hg: Redirect Mercurial stdout/stderr to logging when running as WSGI

Any "console" output from Mercurial when Kallithea is running from WSGI
should end up in Kallithea's logs. That seems like a nice general feature.

This will however also solve another rare but more critical problem:

Mercurial is writing to sys.stdout / sys.stderr, using several layers of
wrapping. Since Mercurial 5.5 (with
https://repo.mercurial-scm.org/hg/rev/8e04607023e5 ), all writes are given a
memoryview.

Apache httpd mod_wsgi is invoking the WSGI with a custom mod_wsgi.Log injected
in sys.stdout / sys.stderr . This logger can however not handle memoryview -
https://github.com/GrahamDumpleton/mod_wsgi/issues/863 .

kallithea/config/application.py

@@ -20,6 +20,7 b' from kallithea.config.middleware.simpleg'
 from kallithea.config.middleware.simplehg import SimpleHg
 from kallithea.config.middleware.wrapper import RequestWrapper
 from kallithea.lib.utils2 import asbool
+from kallithea.lib.vcs.utils import hgcompat
 
 
 __all__ = ['make_app']
@@ -50,6 +51,7 b' def wrap_app(app):'
 def make_app(global_conf, **app_conf):
     """Return WSGI app with logging Mercurial stdout/stderr - to be used as
     Paste or mod_wsgi entry point"""
+    hgcompat.redirect_stdio_to_logging()
     return make_app_raw(global_conf, **app_conf)
 
 

kallithea/lib/vcs/utils/hgcompat.py

@@ -2,10 +2,25 b''
 Mercurial libs compatibility
 """
 
+import logging
+
 import mercurial.encoding
 import mercurial.localrepo
 
 
+class MercurialStdLogger:
+    def __init__(self, logger):
+        self.logger = logger
+
+    def write(self, message):
+        try:
+            self.logger(message.decode().rstrip())
+        except:
+            self.logger(message)
+
+    def flush(self):
+        pass
+
 def monkey_do():
     """Apply some Mercurial monkey patching"""
     # workaround for 3.3 94ac64bcf6fe and not calling largefiles reposetup correctly, and test_archival failing
@@ -15,3 +30,18 b' def monkey_do():'
 
     # Minimize potential impact from custom configuration
     mercurial.encoding.environ[b'HGPLAIN'] = b'1'
+
+
+hglog = logging.getLogger("mercurial")
+
+
+def redirect_stdio_to_logging():
+    # Capture Mercurial stdout/stderr and send to a 'mercurial' logger
+    try:
+        import mercurial.utils.procutil as procutil
+        if not isinstance(procutil.stdout, MercurialStdLogger):
+            procutil.stdout = MercurialStdLogger(hglog.info)
+        if not isinstance(procutil.stderr, MercurialStdLogger):
+            procutil.stderr = MercurialStdLogger(hglog.warning)
+    except Exception as e:
+        hglog.error("Exception installing procutil stdout/stderr: %s", e)