Raise exceptions from except properly

2 files changed, 5 insertions, 5 deletions

diff --git a/otp2289/generator.py b/otp2289/generator.py
index 723ed04..5ea738b 100644
--- a/otp2289/generator.py
+++ b/otp2289/generator.py
@@ -407,7 +407,7 @@ class OTPGenerator:
             hash_algo, step, seed = challenge[4:].split()
             return (seed, hash_algo, int(step))
         except ValueError:
-            raise OTPChallengeException('Invalid challenge')
+            raise OTPChallengeException('Invalid challenge') from None
 
     @staticmethod
     def sha1_digest_folding(sha1_digest):
@@ -506,7 +506,7 @@ class OTPGenerator:
                           tokens]
         except ValueError:
             raise OTPGeneratorException(
-                'One or more words not present in RFC1760')
+                'One or more words not present in RFC1760') from None
         # now we build a string of bits
         bit_stream = format(token_ints[0], '011b')
         bit_stream += format(token_ints[1], '011b')
diff --git a/otp2289/server.py b/otp2289/server.py
index 7322727..d0c3e01 100644
--- a/otp2289/server.py
+++ b/otp2289/server.py
@@ -79,7 +79,7 @@ class OTPState:
             self._hash_algo = OTPGenerator.validate_hash_algo(hash_algo)
             self._step = OTPGenerator.validate_step(current_step)
         except OTPGeneratorException as exp:
-            raise OTPStateException(exp.args[0])
+            raise OTPStateException(exp.args[0]) from None
         self._current_digest = None
         if ot_hex is not None:
             self._current_digest = self.validate_hex(ot_hex)
@@ -166,7 +166,7 @@ class OTPState:
                 return OTPState.validate_hex(response)
             except OTPStateException:
                 raise OTPInvalidResponse(
-                    'The response is neither a valid token or hex')
+                    'The response is neither a valid token or hex') from None
 
     @staticmethod
     def validate_hex(ot_hex):
@@ -192,7 +192,7 @@ class OTPState:
         try:
             return binascii.unhexlify(ot_hex)
         except binascii.Error:
-            raise OTPStateException('Invalid OT-hex')
+            raise OTPStateException('Invalid OT-hex') from None
 
     def get_next_state(self):
         """