test: Exclude asmap.py from Python linter checks

asmap.py, a third-party dependency, is excluded from Python linter checks
because of `from __future__ import annotations` (PEP 563 postponed annotations)
this workaround can be removed when the Python version used is upgraded to 3.7+.

test/lint/lint-python.py

@@ -15,7 +15,10 @@
 
 DEPS = ['flake8', 'mypy', 'pyzmq']
 MYPY_CACHE_DIR = f"{os.getenv('BASE_ROOT_DIR', '')}/test/.mypy_cache"
-FILES_ARGS = ['git', 'ls-files', 'test/functional/*.py', 'contrib/devtools/*.py']
+# asmap.py, a third-party dependency, is excluded from Python linter checks
+# because of `from __future__ import annotations` (PEP 563 postponed annotations)
+# this workaround can be removed when the Python version used is upgraded to 3.7+.
+EXCLUDED = ['contrib/seeds/asmap.py']
 
 ENABLED = (
     'E101,'  # indentation contains mixed spaces and tabs
@@ -103,10 +106,11 @@ def check_dependencies():
 def main():
     check_dependencies()
 
+    exclude_args = [":(exclude)" + p for p in EXCLUDED]
     if len(sys.argv) > 1:
         flake8_files = sys.argv[1:]
     else:
-        files_args = ['git', 'ls-files', '*.py']
+        files_args = ['git', 'ls-files', '*.py'] + exclude_args
         flake8_files = subprocess.check_output(files_args).decode("utf-8").splitlines()
 
     flake8_args = ['flake8', '--ignore=B,C,E,F,I,N,W', f'--select={ENABLED}'] + flake8_files
@@ -118,7 +122,8 @@ def main():
     except subprocess.CalledProcessError:
         exit(1)
 
-    mypy_files = subprocess.check_output(FILES_ARGS).decode("utf-8").splitlines()
+    files_args = ['git', 'ls-files', 'test/functional/*.py', 'contrib/devtools/*.py'] + exclude_args
+    mypy_files = subprocess.check_output(files_args).decode("utf-8").splitlines()
     mypy_args = ['mypy', '--show-error-codes'] + mypy_files
 
     try: