Allow FieldSkipLogFilter to handle exception records

Resolves #1035

CHANGES.txt

@@ -14,6 +14,8 @@ Changes:
 
 Bug fixes:
 
+- Allow FieldSkipLogFilter to handle exception messages as well as strings
+  (reported in #1035).
 - Clean up VSI files left by MemoryFileBase, resolving #1041.
 - Hard-coded "utf-8" collection encoding added in #423 has been removed
   (#1057).

fiona/logutils.py

@@ -9,14 +9,14 @@ class FieldSkipLogFilter(logging.Filter):
     At most, one message per field skipped per loop will be passed.
     """
 
-    def __init__(self, name=''):
+    def __init__(self, name=""):
         super(FieldSkipLogFilter, self).__init__(name)
         self.seen_msgs = set()
 
     def filter(self, record):
         """Pass record if not seen."""
-        if getattr(record, 'msg', "").startswith("Skipping field"):
-            msg = record.getMessage()
+        msg = record.getMessage()
+        if msg.startswith("Skipping field"):
             retval = msg not in self.seen_msgs
             self.seen_msgs.add(msg)
             return retval
@@ -25,7 +25,6 @@ def filter(self, record):
 
 
 class LogFiltering(object):
-
     def __init__(self, logger, filter):
         self.logger = logger
         self.filter = filter

tests/test_logutils.py

@@ -16,6 +16,7 @@ def test_filtering(caplog):
         logger.warning("Skipping field 2")
         logger.warning("Danger!")
         logger.warning("Skipping field 1")
+
     assert len(caplog.records) == 4
     assert caplog.records[0].getMessage() == "Attention!"
     assert caplog.records[1].getMessage() == "Skipping field 1"
@@ -39,3 +40,13 @@ def test_skipping_list(caplog, data_dir):
     assert len(results) == 3
     assert not any(['skip_me' in f['properties'] for f in results])
     assert len([rec for rec in caplog.records if rec.getMessage().startswith('Skipping')]) == 1
+
+
+def test_log_filter_exception(caplog):
+    """FieldSkipLogFilter handles exceptions from log.exception()."""
+    logger = logging.getLogger()
+    with LogFiltering(logger, FieldSkipLogFilter()):
+        logger.exception(ValueError("Oh no"))
+
+    assert len(caplog.records) == 1
+    assert caplog.records[0].getMessage() == "Oh no"