Add an exception for malformed expected output in functional tests

1 files changed, 20 insertions, 2 deletions

diff --git a/pylint/testutils/output_line.py b/pylint/testutils/output_line.py
index 8bf5b7124..17507e2d3 100644
--- a/pylint/testutils/output_line.py
+++ b/pylint/testutils/output_line.py
@@ -22,6 +22,21 @@ class Message(
     __hash__ = None
 
 
+class MalformedOutputLineException(Exception):
+    def __init__(self, row, exception):
+        example = "msg-symbolic-name:42:MyClass.my_function:The message"
+        other_example = "msg-symbolic-name:7::The message"
+        reconstructed_row = ":".join(row)
+        msg = "Expected '{example}' or '{other_example}' but we got '{reconstructed_row}'".format(
+            example=example,
+            other_example=other_example,
+            reconstructed_row=reconstructed_row,
+        )
+        Exception.__init__(
+            self, "{msg}: {exception}".format(msg=msg, exception=exception)
+        )
+
+
 class OutputLine(
     collections.namedtuple(
         "OutputLine", ["symbol", "lineno", "object", "msg", "confidence"]
@@ -41,8 +56,11 @@ class OutputLine(
 
     @classmethod
     def from_csv(cls, row):
-        confidence = row[4] if len(row) == 5 else interfaces.HIGH.name
-        return cls(row[0], int(row[1]), row[2], row[3], confidence)
+        try:
+            confidence = row[4] if len(row) == 5 else interfaces.HIGH.name
+            return cls(row[0], int(row[1]), row[2], row[3], confidence)
+        except Exception as e:
+            raise MalformedOutputLineException(row, e) from e
 
     def to_csv(self):
         if self.confidence == interfaces.HIGH.name: