Problem
Resource not found: datasets/None'
Solution
If you are using the Access ECMWF Public Datasets service and you get this error it means that the mandatory keyword "dataset" is not set. Review the request and add this keyword. Example:
'dataset' : "interim",
If you are not trying to access Public Datasets (and you are an ECMWF member), please check How to use Python requests to retrieve data from the Access MARS service - Web API FAQ