Handle insufficient driver gracefully (facebookresearch#4271)

Summary:
Gracefully handle insufficient drivers (ex. no driver available.)

Resolves facebookresearch#4251

Pull Request resolved: facebookresearch#4271

Reviewed By: mnorris11

Differential Revision: D72351969

Pulled By: ramilbakhshyiev

fbshipit-source-id: de2b6f741087c59665e7f9f171ee6096c7eea39b

Author: JAicewizard

faiss/gpu/utils/DeviceUtils.cu

@@ -30,7 +30,7 @@ void setCurrentDevice(int device) {
 int getNumDevices() {
     int numDev = -1;
     cudaError_t err = cudaGetDeviceCount(&numDev);
-    if (cudaErrorNoDevice == err) {
+    if (cudaErrorNoDevice == err || cudaErrorInsufficientDriver == err) {
         numDev = 0;
     } else {
         CUDA_VERIFY(err);