Schema with no required fields crashes

[daliaMarzouk90]

I am using marshmellow schema in generating swagger documentation. When I am trying to create a schema without required fields the code crashes

if len(definitions[v.__name__]['required']) != 0:
                    new[k][0]['required'] = True

How to avoid this problem

[yswf]

You can determine whether the key exists, modify the source code

if 'required' in definitions[v.__name__] and len(definitions[v.__name__]['required']) != 0:
    new[k][0]['required'] = True