[Fix] avoid get_local_path bc-breaking (#6719)

* [Fix] avoid get_local_path bc-breaking

* avoid mmcv.FileClient.get_local_path bc-breaking

* avoid mmcv.FileClient.get_local_path bc-breaking

* avoid mmcv.FileClient.get_local_path bc-breaking

* Update custom.py

* Update custom.py

* fix lint

Author: BIGWangYuDong

mmdet/datasets/custom.py

@@ -88,13 +88,29 @@ def __init__(self,
                 self.proposal_file = osp.join(self.data_root,
                                               self.proposal_file)
         # load annotations (and proposals)
-        with self.file_client.get_local_path(self.ann_file) as local_path:
-            self.data_infos = self.load_annotations(local_path)
+        if hasattr(self.file_client, 'get_local_path'):
+            with self.file_client.get_local_path(self.ann_file) as local_path:
+                self.data_infos = self.load_annotations(local_path)
+        else:
+            warnings.warn(
+                'The used MMCV version does not have get_local_path. '
+                f'We treat the {self.ann_file} as local paths and it '
+                'might cause errors if the path is not a local path. '
+                'Please use MMCV>= 1.3.16 if you meet errors.')
+            self.data_infos = self.load_annotations(self.ann_file)
 
         if self.proposal_file is not None:
-            with self.file_client.get_local_path(
-                    self.proposal_file) as local_path:
-                self.proposals = self.load_proposals(local_path)
+            if hasattr(self.file_client, 'get_local_path'):
+                with self.file_client.get_local_path(
+                        self.proposal_file) as local_path:
+                    self.proposals = self.load_proposals(local_path)
+            else:
+                warnings.warn(
+                    'The used MMCV version does not have get_local_path. '
+                    f'We treat the {self.ann_file} as local paths and it '
+                    'might cause errors if the path is not a local path. '
+                    'Please use MMCV>= 1.3.16 if you meet errors.')
+                self.proposals = self.load_proposals(self.proposal_file)
         else:
             self.proposals = None