ui: don't show exception for "Too many files" error

iterative/dvc.org#875 (comment)

Stops showing the exception in non-verbose mode, but shows full
traceback in verbose mode.

Introducing our custom parameter `tb_only` through standard `extra`
logging parameter.

dvc/logger.py

@@ -62,7 +62,7 @@ def format(self, record):
             return record.msg
 
         if record.levelname == "ERROR" or record.levelname == "CRITICAL":
-            exception, stack_trace = self._parse_exc(record.exc_info)
+            exception, stack_trace = self._parse_exc(record)
 
             return (
                 "{color}{levelname}{nc}: {description}" "{stack_trace}\n"
@@ -122,13 +122,15 @@ def _walk_exc(self, exc_info):
 
         return exc_list, tb_list
 
-    def _parse_exc(self, exc_info):
-        if not exc_info:
+    def _parse_exc(self, record):
+        tb_only = getattr(record, "tb_only", False)
+
+        if not record.exc_info:
             return (None, "")
 
-        exc_list, tb_list = self._walk_exc(exc_info)
+        exc_list, tb_list = self._walk_exc(record.exc_info)
 
-        exception = ": ".join(exc_list)
+        exception = None if tb_only else ": ".join(exc_list)
 
         if self._current_level() == logging.DEBUG:
             stack_trace = (

dvc/main.py

@@ -60,7 +60,8 @@ def main(argv=None):
     except Exception as exc:  # pylint: disable=broad-except
         if isinstance(exc, OSError) and exc.errno == errno.EMFILE:
             logger.exception(
-                "too many open files, please increase your `ulimit`"
+                "too many open files, please increase your `ulimit`",
+                extra={"tb_only": True},
             )
         else:
             logger.exception("unexpected error")

tests/unit/test_logger.py

@@ -102,6 +102,25 @@ def test_exception_under_verbose(self, caplog):
 
             assert expected == formatter.format(caplog.records[0])
 
+    def test_tb_only(self, caplog):
+        with caplog.at_level(logging.DEBUG, logger="dvc"):
+            try:
+                raise Exception("description")
+            except Exception:
+                stack_trace = traceback.format_exc()
+                logger.exception("something", extra={"tb_only": True})
+
+            expected = (
+                "{red}ERROR{nc}: something\n"
+                "{red}{line}{nc}\n"
+                "{stack_trace}"
+                "{red}{line}{nc}\n".format(
+                    line="-" * 60, stack_trace=stack_trace, **colors
+                )
+            )
+
+            assert expected == formatter.format(caplog.records[0])
+
     def test_nested_exceptions(self, caplog):
         with caplog.at_level(logging.DEBUG, logger="dvc"):
             try: