Fix typing annotations for python 3.8

Queue does not accept type annotations and the tests running pytest was failing with
```
python -m pytest
...
opensfm/features_processing.py:19: in <module>
    ProcessQueue = queue.Queue[
E   TypeError: 'type' object is not subscriptable
...
```

Similar problem for networkx EdgeView

Author: paulinus

opensfm/features_processing.py

@@ -4,6 +4,7 @@
 import math
 import queue
 import threading
+import sys
 from timeit import default_timer as timer
 from typing import Any, cast, Dict, List, Optional, Tuple, Union
 
@@ -16,11 +17,16 @@
 
 logger: logging.Logger = logging.getLogger(__name__)
 
-ProcessQueue = queue.Queue[
-    Optional[
-        Tuple[str, NDArray, Optional[NDArray], Optional[NDArray], DataSetBase, bool]
+
+if sys.version_info >= (3, 9):
+    ProcessQueue = queue.Queue[
+        Optional[
+            Tuple[str, "NDArray", Optional["NDArray"], Optional["NDArray"], DataSetBase, bool]
+        ]
     ]
-]
+else:
+    ProcessQueue = queue.Queue
+
 ProducerArgs = Tuple[
     ProcessQueue,
     DataSetBase,

opensfm/large/tools.py

@@ -1,4 +1,5 @@
 # pyre-strict
+from __future__ import annotations
 import itertools
 import logging
 from functools import lru_cache