the check_cert_signature() method was attempting to compare RSA and ECC signatures.

If a ec public-key certificate is signed with an RSA key, then it can't be a self-signed certificate, in which case we just raise InvalidSignature.

lemur/common/utils.py

@@ -199,6 +199,8 @@ def is_selfsigned(cert):
         return True
     except InvalidSignature:
         return False
+    except UnsupportedAlgorithm as e:
+        raise Exception(e)
 
 
 def is_weekend(date):