Added brief note about why issue 387 tests are invoked the way they are.

Author: hategan

tests/test_issue_387_1.run

@@ -1,3 +1,6 @@
+# This test must be run in a separate process, since it is sensitive
+# to threading and process context.
+
 import logging
 import os
 from multiprocessing import Process, set_start_method

tests/test_issue_387_2.run

@@ -1,3 +1,6 @@
+# This test must be run in a separate process, since it is sensitive
+# to threading and process context.
+
 import logging
 from threading import Thread
 import psij

tests/test_issue_387_3.run

@@ -1,3 +1,6 @@
+# This test must be run in a separate process, since it is sensitive
+# to threading and process context.
+
 import logging
 from threading import Thread
 import psij