botocore exceptions are not picklable

they need to take a “msg” argument, and all other arguments must be optional:

http://stackoverflow.com/questions/16244923/how-to-make-a-custom-exception-class-with-multiple-init-args-pickleable. I’ve attempted fixing this in PR: https://github.com/boto/botocore/pull/835

simple testcase:

try:
    raise botocore.exceptions.NoCredentialsError
except Exception as e:
    b = pickle.dumps(e)
    e = pickle.loads(b)

[jezdez]

@thehesiod I’ve opened #1191 that uses __reduce__ and which also tackles #899 to have a consistent exception error set. Bonus feature is being able to import the exception classes under botocore.exceptions.<service>.<exceptioncls>, e.g. as botocore.exceptions.s3.BucketAlreadyExists

[thehesiod]

this is now further compounded by the metaclass instantiation of ClientError, which return things like botocore.errorfactory.NoSuchKey, which can’t pickle because that class does not exist in that module. I think a better impl is probably implementing the __reduce__ methods