check if Darshan log file exists

Author: wkliao

darshan-test/python_runtime_tests.py

@@ -274,14 +274,19 @@ def test_os_dup(tmpdir):
         io_module = "POSIX"
         key = "POSIX_BYTES_WRITTEN"
 
+        # check if log file exists
+        if not os.path.isfile(path_to_log) :
+            print(f"Darshan log file '{path_to_log}' does not exist")
+        else :
+            print(f"Darshan log file '{path_to_log}'")
+
         try:
             with darshan.DarshanReport(path_to_log, filter_patterns=[target_filename], filter_mode='include') as report:
                 try:
                     records = report.records[io_module].to_dict()
                     if len(records) > 0:
-                        rec = report.records[io_module].to_dict()
                         try:
-                            value = rec[0]["counters"][key]
+                            value = records[0]["counters"][key]
                             print(f"key '{key}' has value of '{value}'")
                             assert value == 928
                         except KeyError: