iotests/297: split test into sub-cases

Take iotest 297's main() test function and split it into two sub-cases
that can be skipped individually. We can also drop custom environment
setup from the pylint test as it isn't needed.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-id: 20211019144918.3159078-11-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

tests/qemu-iotests/297

@@ -82,36 +82,51 @@ def run_linter(
     )
 
 
-def main() -> None:
-    for linter in ('pylint', 'mypy'):
-        try:
-            run_linter(linter, ['--version'], suppress_output=True)
-        except subprocess.CalledProcessError:
-            iotests.notrun(f"'{linter}' not found")
-
-    files = get_test_files()
-
-    iotests.logger.debug('Files to be checked:')
-    iotests.logger.debug(', '.join(sorted(files)))
+def check_linter(linter: str) -> bool:
+    try:
+        run_linter(linter, ['--version'], suppress_output=True)
+    except subprocess.CalledProcessError:
+        iotests.case_notrun(f"'{linter}' not found")
+        return False
+    return True
 
-    env = os.environ.copy()
-    env['MYPYPATH'] = env['PYTHONPATH']
 
+def test_pylint(files: List[str]) -> None:
     print('=== pylint ===')
     sys.stdout.flush()
-    try:
-        run_linter('pylint', files, env=env)
-    except subprocess.CalledProcessError:
-        # pylint failure will be caught by diffing the IO.
-        pass
 
+    if not check_linter('pylint'):
+        return
+
+    run_linter('pylint', files)
+
+
+def test_mypy(files: List[str]) -> None:
     print('=== mypy ===')
     sys.stdout.flush()
-    try:
-        run_linter('mypy', files, env=env, suppress_output=True)
-    except subprocess.CalledProcessError as exc:
-        if exc.output:
-            print(exc.output)
+
+    if not check_linter('mypy'):
+        return
+
+    env = os.environ.copy()
+    env['MYPYPATH'] = env['PYTHONPATH']
+
+    run_linter('mypy', files, env=env, suppress_output=True)
+
+
+def main() -> None:
+    files = get_test_files()
+
+    iotests.logger.debug('Files to be checked:')
+    iotests.logger.debug(', '.join(sorted(files)))
+
+    for test in (test_pylint, test_mypy):
+        try:
+            test(files)
+        except subprocess.CalledProcessError as exc:
+            # Linter failure will be caught by diffing the IO.
+            if exc.output:
+                print(exc.output)
 
 
 iotests.script_main(main)