pylint 2.2: Fix unnecessary pass statement

pylint 2.2.0 has a new checker for unnecessary pass statements. There is
no need to have a pass statement in functions or classes with a doc
string.

Fixes: https://pagure.io/freeipa/issue/7772
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Thomas Woerner <twoerner@redhat.com>

ipaserver/p11helper.py

@@ -521,23 +521,20 @@ CONST_RSA_PKCS_OAEP_PARAMS_ptr = new_ptr(CK_RSA_PKCS_OAEP_PARAMS, dict(
 #
 class P11HelperException(Exception):
     """parent class for all exceptions"""
-    pass
+
 P11HelperException.__name__ = 'Exception'
 
 
 class Error(P11HelperException):
     """general error"""
-    pass
 
 
 class NotFound(P11HelperException):
     """key not found"""
-    pass
 
 
 class DuplicationError(P11HelperException):
     """key already exists"""
-    pass
 
 
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