Add test for duplicate headers

1 files changed, 6 insertions, 0 deletions

diff --git a/quality_control/errors.py b/quality_control/errors.py
index 758a300..993748c 100644
--- a/quality_control/errors.py
+++ b/quality_control/errors.py
@@ -12,6 +12,12 @@ class InvalidHeaderValue(Exception):
     def __init__(self, *args):
         super().__init__(self, *args)
 
+class DuplicateHeader(Exception):
+    """Raised when a header contains 2 similar headers."""
+
+    def __init__(self, *args):
+        super().__init__(self, *args)
+
 class ParseError(Exception):
     def __init(self, *args):
         super().__init__(*args)