text: # Copyright 2013 Donald Stufft and individual contributors
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  # http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  from __future__ import absolute_import, division, print_function
  
  
  class CryptoError(Exception):
      """
      Base exception for all nacl related errors
      """
  
  
  class BadSignatureError(CryptoError):
      """
      Raised when the signature was forged or otherwise corrupt.
      """
  
  
  class RuntimeError(RuntimeError, CryptoError):
      pass
  
  
  class AssertionError(AssertionError, CryptoError):
      pass
  
  
  class TypeError(TypeError, CryptoError):
      pass
  
  
  class ValueError(ValueError, CryptoError):
      pass
  
  
  class InvalidkeyError(CryptoError):
      pass
  
  
  class CryptPrefixError(InvalidkeyError):
      pass
  
  
  class UnavailableError(RuntimeError):
      """
      is a subclass of :class:`~nacl.exceptions.RuntimeError`, raised when
      trying to call functions not available in a minimal build of
      libsodium.
      """
      pass
  
  
  def ensure(cond, *args, **kwds):
      """
      Return if a condition is true, otherwise raise a caller-configurable
      :py:class:`Exception`
      :param bool cond: the condition to be checked
      :param sequence args: the arguments to be passed to the exception's
                            constructor
      The only accepted named parameter is `raising` used to configure the
      exception to be raised if `cond` is not `True`
      """
      _CHK_UNEXP = 'check_condition() got an unexpected keyword argument {0}'
  
      raising = kwds.pop('raising', AssertionError)
      if kwds:
          raise TypeError(_CHK_UNEXP.format(repr(kwds.popitem()[0])))
  
      if cond is True:
          return
      raise raising(*args)
  