Three months valid Residency card for application

I'm an Algerian PHD student in France, holding a French residency card mention"Scientific" expiring in 2 and 1/2 months. When I applied for 1 entry Visa between 2nd and 9th of August for a conference in shanghai , my application has been rejected. the reason behind that is that the embassy requires 6 months validity of the residency card while applying.

My concern is the fact that this 6 months validity is no where mentioned in the required documents.