* The elements of the GrandTypes enum have been renamed to screaming snake case.
* A warning is raised, if a second TokenResource is created
with a different token storage than the first one.
* Errors from txoauth2 are now real exceptions and should now be thrown instead of returned in
OAuth2.onAuthenticate, TokenResource.onCustomGrantTypeRequest & ClientStorage.authenticateClient.
* ServerError now takes an optional message parameter.
* If the TokenFactory generates an invalid token,
a ServerError is now returned instead of a ScopeError.
* TokenResource.getTokenStorageSingleton now raises a RuntimeError
instead of a ValueError if no singleton was registered.
* TokenStorage.hasAccess must now also accept a single scope.
* Errors with 401 return code now always add a WWW-Authenticate header.
* Removed OAuth2RequestError and UnauthorizedOAuth2Error classes, these are now just OAuth2Errors.
* OAuth2Error got new optional parameters scope, addWwwAuthenticateHeader and authScheme.
* Renamed some attributes of the OAuth2Errors: message -> name, detail -> description.
* The position of the keyword argument state and errorUri switched for AuthorizationErrors
* Errors now validate their parameters. The OAuth2 spec only permits certain characters in the name,
description, scope and errorUris. Any invalid characters will be replaced by a question mark.