Do not download TRAIN.WEIGHTS in infer_simple.py & infer.py

Summary:
Before this change <code>assert_and_infer_cfg</code> would override the weights passed by the user with CFG ones.

It is normal to change it as the user is required to pass weights, otherwise there will be this error :
<code>AssertionError: <class 'NoneType'></code>. (verified only in infer_simple.py)

Sort of follow-up of eddb1301.
Closes https://github.com/facebookresearch/Detectron/pull/331

Reviewed By: ir413

Differential Revision: D7569224

Pulled By: rbgirshick

fbshipit-source-id: 00dbaadd2440f39b2b3440b4101a58ed3e68a908

tools/infer.py

@@ -105,7 +105,7 @@ def get_rpn_box_proposals(im, args):
     cfg.MODEL.RPN_ONLY = True
     cfg.TEST.RPN_PRE_NMS_TOP_N = 10000
     cfg.TEST.RPN_POST_NMS_TOP_N = 2000
-    assert_and_infer_cfg()
+    assert_and_infer_cfg(cache_urls=False)
 
     model = model_engine.initialize_model_from_cfg(args.rpn_pkl)
     with c2_utils.NamedCudaScope(0):
@@ -137,7 +137,7 @@ def main(args):
         else:
             weights_file = cfg.TEST.WEIGHTS
         cfg.NUM_GPUS = 1
-        assert_and_infer_cfg()
+        assert_and_infer_cfg(cache_urls=False)
         model = model_engine.initialize_model_from_cfg(weights_file)
         with c2_utils.NamedCudaScope(0):
             cls_boxes_, cls_segms_, cls_keyps_ = \

tools/infer_simple.py

@@ -96,7 +96,7 @@ def main(args):
     merge_cfg_from_file(args.cfg)
     cfg.NUM_GPUS = 1
     args.weights = cache_url(args.weights, cfg.DOWNLOAD_CACHE)
-    assert_and_infer_cfg()
+    assert_and_infer_cfg(cache_urls=False)
     model = infer_engine.initialize_model_from_cfg(args.weights)
     dummy_coco_dataset = dummy_datasets.get_coco_dataset()