all exceptions inherit from PyJwtError (jpadilla#340)

* all exceptions inherit from PyJwtError

* s/Jwt/JWT/

* add to init

Author: dradetsky

jwt/__init__.py

@@ -27,4 +27,5 @@
     InvalidIssuedAtError, InvalidIssuerError, ExpiredSignature,
     InvalidAudience, InvalidIssuer, MissingRequiredClaimError,
     InvalidSignatureError,
+    PyJWTError,
 )

jwt/exceptions.py

@@ -1,4 +1,11 @@
-class InvalidTokenError(Exception):
+class PyJWTError(Exception):
+    """
+    Base class for all exceptions
+    """
+    pass
+
+
+class InvalidTokenError(PyJWTError):
     pass
 
 
@@ -30,7 +37,7 @@ class ImmatureSignatureError(InvalidTokenError):
     pass
 
 
-class InvalidKeyError(Exception):
+class InvalidKeyError(PyJWTError):
     pass