MAINT: PR 839 revisions

* the testsuite now always uses `DarshanReport` with a context
manager to avoid shenanigans with `__del__` and garbage
collection/`pytest`/multiple threads

* this appears to fix the problem with testsuite hangs
described in gh-839 and gh-851

darshan-util/pydarshan/darshan/tests/test_summary.py

@@ -236,11 +236,11 @@ def test_main_all_logs_repo_files(tmpdir, log_filepath):
                     else:
                         assert actual_runtime_heatmap_titles == 0
 
-                # check for presence of bandwidth summary strings
-                # (more detailed per-module probes are present
-                # in test_derived_metrics_bytes_and_bandwidth())
-                assert "I/O performance estimate" in report_str
-                assert "color: blue" in report_str
+                    # check for presence of bandwidth summary strings
+                    # (more detailed per-module probes are present
+                    # in test_derived_metrics_bytes_and_bandwidth())
+                    assert "I/O performance estimate" in report_str
+                    assert "color: blue" in report_str
 
 
 class TestReportData: