mark_process_dead: avoid error with bad env

When the multiprocess environemnt is not properly set-up (missing
environment variable) and mark_process_dead is called, the method raises
an error on path.join() because the path is None which may be
problematic

This commit simply ignores the cleanup when the variable is not present

Author: romuald

prometheus_client/multiprocess.py

@@ -156,6 +156,11 @@ def mark_process_dead(pid, path=None):
     """Do bookkeeping for when one process dies in a multi-process setup."""
     if path is None:
         path = os.environ.get('PROMETHEUS_MULTIPROC_DIR', os.environ.get('prometheus_multiproc_dir'))
+
+    if path is None:
+        # Avoid error when environment is not correctly set-up
+        return
+
     for f in glob.glob(os.path.join(path, f'gauge_livesum_{pid}.db')):
         os.remove(f)
     for f in glob.glob(os.path.join(path, f'gauge_liveall_{pid}.db')):

tests/test_multiprocess.py

@@ -60,7 +60,7 @@ def _value_class(self):
         return
 
     def tearDown(self):
-        del os.environ['PROMETHEUS_MULTIPROC_DIR']
+        os.environ.pop('PROMETHEUS_MULTIPROC_DIR', None)
         shutil.rmtree(self.tempdir)
         values.ValueClass = MutexValue
 
@@ -303,6 +303,11 @@ def test_missing_gauge_file_during_merge(self):
             os.path.join(self.tempdir, 'gauge_livesum_9999999.db'),
         ]))
 
+    def test_mark_dead_no_env(self):
+        del os.environ['PROMETHEUS_MULTIPROC_DIR']
+
+        mark_process_dead(123)
+
 
 class TestMmapedDict(unittest.TestCase):
     def setUp(self):