Remove unused loop variables (#2935)

This comes from flake8-bugbear branch, working towards eliminating
bugbear B007 errors there.

This PR does not address B007 errors in visualization or in the
test suite.

parsl/executors/high_throughput/interchange.py

@@ -205,7 +205,7 @@ def get_tasks(self, count):
             eg. [{'task_id':<x>, 'buffer':<buf>} ... ]
         """
         tasks = []
-        for i in range(0, count):
+        for _ in range(0, count):
             try:
                 x = self.pending_task_queue.get(block=False)
             except queue.Empty:
@@ -518,7 +518,7 @@ def process_results_incoming(self, interesting_managers, hub_channel):
 
                 got_result = False
                 m = self._ready_managers[manager_id]
-                for (b_message, r) in b_messages:
+                for (_, r) in b_messages:
                     assert 'type' in r, f"Message is missing type entry: {r}"
                     if r['type'] == 'result':
                         got_result = True

parsl/executors/high_throughput/zmq_pipes.py

@@ -53,7 +53,7 @@ def run(self, message, max_retries=3):
         """
         reply = '__PARSL_ZMQ_PIPES_MAGIC__'
         with self._lock:
-            for i in range(max_retries):
+            for _ in range(max_retries):
                 try:
                     self.zmq_socket.send_pyobj(message, copy=True)
                     reply = self.zmq_socket.recv_pyobj()

parsl/executors/status_handling.py

@@ -193,7 +193,7 @@ def scale_out(self, blocks: int = 1) -> List[str]:
             raise ScalingFailed(self, "No execution provider available")
         block_ids = []
         logger.info(f"Scaling out by {blocks} blocks")
-        for i in range(blocks):
+        for _ in range(blocks):
             block_id = str(self._block_id_counter.get_id())
             logger.info(f"Allocated block ID {block_id}")
             try:

parsl/utils.py

@@ -128,7 +128,7 @@ def get_std_fname_mode(
 
 @contextmanager
 def wait_for_file(path: str, seconds: int = 10) -> Generator[None, None, None]:
-    for i in range(0, int(seconds * 100)):
+    for _ in range(0, int(seconds * 100)):
         time.sleep(seconds / 100.)
         if os.path.exists(path):
             break