Log exceptions (Fixes #447)

Exceptions were just written to stderr but not into logs.

radicale/__init__.py

@@ -28,6 +28,7 @@ should have been included in this package.
 
 import base64
 import contextlib
+import io
 import itertools
 import os
 import posixpath
@@ -130,9 +131,29 @@ class ThreadedHTTPSServer(socketserver.ThreadingMixIn, HTTPSServer):
 
 class RequestHandler(wsgiref.simple_server.WSGIRequestHandler):
     """HTTP requests handler."""
+
+    # These class attributes must be set before creating instance
+    logger = None
+
+    def __init__(self, *args, **kwargs):
+        # Store exception for logging
+        self.error_stream = io.StringIO()
+        super().__init__(*args, **kwargs)
+
+    def get_stderr(self):
+        return self.error_stream
+
     def log_message(self, *args, **kwargs):
         """Disable inner logging management."""
 
+    def handle(self):
+        super().handle()
+        # Log exception
+        error = self.error_stream.getvalue().strip("\n")
+        if error:
+            self.logger.error("An exception occurred during request:\n" +
+                              error)
+
 
 class Application:
     """WSGI application managing collections."""