properly handled failed seek

requests/utils.py

@@ -92,14 +92,16 @@ def super_len(o):
         else:
             if hasattr(o, 'seek') and total_length is None:
                 # StringIO and BytesIO have seek but no useable fileno
+                try:
+                    # seek to end of file
+                    o.seek(0, 2)
+                    total_length = o.tell()
 
-                # seek to end of file
-                o.seek(0, 2)
-                total_length = o.tell()
-
-                # seek back to current position to support
-                # partially read file-like objects
-                o.seek(current_position or 0)
+                    # seek back to current position to support
+                    # partially read file-like objects
+                    o.seek(current_position or 0)
+                except (OSError, IOError):
+                    total_length = 0
 
     if total_length is None:
         total_length = 0

tests/test_requests.py

@@ -1546,7 +1546,7 @@ class TestRequests:
             def tell(self):
                 return 0
 
-            def seek(self, pos):
+            def seek(self, pos, whence=0):
                 raise OSError()
 
             def __iter__(self):