Fixed #34810 -- Measured test coverage on django-admin commands.

tests/.coveragerc

@@ -1,7 +1,7 @@
 [run]
 branch = True
 concurrency = multiprocessing,thread
-data_file = .coverages/.coverage
+data_file = ${RUNTESTS_DIR-.}/.coverages/.coverage
 omit =
     */django/utils/autoreload.py
 source = django

tests/runtests.py

@@ -71,6 +71,10 @@ tempfile.tempdir = os.environ["TMPDIR"] = TMPDIR
 # Removing the temporary TMPDIR.
 atexit.register(shutil.rmtree, TMPDIR)
 
+# Add variables enabling coverage to trace code in subprocesses.
+os.environ["RUNTESTS_DIR"] = RUNTESTS_DIR
+os.environ["COVERAGE_PROCESS_START"] = os.path.join(RUNTESTS_DIR, ".coveragerc")
+
 
 # This is a dict mapping RUNTESTS_DIR subdirectory to subdirectories of that
 # directory to skip when searching for test modules.

tests/sitecustomize.py

@@ -0,0 +1,6 @@
+try:
+    import coverage
+except ImportError:
+    pass
+else:
+    coverage.process_startup()