Fix #10554. Added context manager support to Popen objects.

Added a few common Popen uses to the tests like we've done for a few other
instances of adding context managers. Eventually the entire test suite
could be converted to use the context manager format.
diff --git a/Misc/NEWS b/Misc/NEWS
index e856c6d..434ed23 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -58,6 +58,8 @@
 Library
 -------
 
+- Issue #10554: Add context manager support to subprocess.Popen objects.
+
 - Issue #8989: email.utils.make_msgid now has a domain parameter that can
   override the domain name used in the generated msgid.