Update precommit flake8 (#3961)

* fix flake8 errors

* update flake8 hook

* update flake8 plugins

.pre-commit-config.yaml

         files: "gym-unity/.*"
         args: [--ignore-missing-imports, --disallow-incomplete-defs]
 
+-   repo: https://gitlab.com/pycqa/flake8
+    rev: 3.8.1
+    hooks:
+    -   id: flake8
+        exclude: >
+            (?x)^(
+                .*_pb2.py|
+                .*_pb2_grpc.py
+            )$
+        # flake8-tidy-imports is used for banned-modules, not actually tidying
+        additional_dependencies: [flake8-comprehensions==3.2.2, flake8-tidy-imports==4.1.0, flake8-bugbear==20.1.4]
+
-    rev: v2.4.0
+    rev: v2.5.0
     hooks:
     -   id: mixed-line-ending
         exclude: >
                 .*.meta
             )$
         args: [--fix=lf]
-    -   id: flake8
-        exclude: >
-            (?x)^(
-                .*_pb2.py|
-                .*_pb2_grpc.py
-            )$
-        # flake8-tidy-imports is used for banned-modules, not actually tidying
-        additional_dependencies: [flake8-comprehensions==3.1.4, flake8-tidy-imports==4.0.0, flake8-bugbear==20.1.2]
+
     -   id: trailing-whitespace
         name: trailing-whitespace-markdown
         types: [markdown]

ml-agents/mlagents/trainers/ppo/trainer.py

             self.update_buffer.shuffle(sequence_length=self.policy.sequence_length)
             buffer = self.update_buffer
             max_num_batch = buffer_length // batch_size
-            for l in range(0, max_num_batch * batch_size, batch_size):
+            for i in range(0, max_num_batch * batch_size, batch_size):
-                    buffer.make_mini_batch(l, l + batch_size), n_sequences
+                    buffer.make_mini_batch(i, i + batch_size), n_sequences
                 )
                 for stat_name, value in update_stats.items():
                     batch_update_stats[stat_name].append(value)

ml-agents/mlagents/trainers/subprocess_env_manager.py

         return self.env_workers[0].recv().payload
 
     def close(self) -> None:
-        logger.debug(f"SubprocessEnvManager closing.")
+        logger.debug("SubprocessEnvManager closing.")
         self.step_queue.close()
         self.step_queue.join_thread()
         for env_worker in self.env_workers:

ml-agents/tests/yamato/check_coverage_percent.py

         # Rather than try to parse the XML, just look for a line of the form
         # <Linecoverage>73.9</Linecoverage>
         lines = f.readlines()
-        for l in lines:
-            if "Linecoverage" in l:
-                pct = l.replace("<Linecoverage>", "").replace("</Linecoverage>", "")
+        for line in lines:
+            if "Linecoverage" in line:
+                pct = line.replace("<Linecoverage>", "").replace("</Linecoverage>", "")
                 pct = float(pct)
                 if pct < min_percentage:
                     print(

ml-agents/tests/yamato/yamato_utils.py

     subprocess.check_call("git reset HEAD .", shell=True)
     subprocess.check_call("git checkout -- .", shell=True)
     # Ensure the cache isn't polluted with old compiled assemblies.
-    subprocess.check_call(f"rm -rf Project/Library", shell=True)
+    subprocess.check_call("rm -rf Project/Library", shell=True)
 
 
 def override_config_file(src_path, dest_path, **kwargs):

utils/validate_versions.py

 
 def extract_version_string(filename):
     with open(filename) as f:
-        for l in f.readlines():
-            if l.startswith(VERSION_LINE_START):
-                return l.replace(VERSION_LINE_START, "").strip()
+        for line in f.readlines():
+            if line.startswith(VERSION_LINE_START):
+                return line.replace(VERSION_LINE_START, "").strip()
     return None