Made the test runner try multiple port numbers for the SMTP server, in order to handle the case where multiple test suites are in progress on the same host (which can happen when multiple buildbot slaves are running tests at the same time).

- Legacy-Id: 9186

ietf/utils/test_runner.py

@@ -352,8 +352,20 @@ class IetfTestRunner(DiscoverRunner):
 
         assert not settings.IDTRACKER_BASE_URL.endswith('/')
 
-        self.smtpd_driver = SMTPTestServerDriver((ietf.utils.mail.SMTP_ADDR['ip4'],ietf.utils.mail.SMTP_ADDR['port']),None) 
-        self.smtpd_driver.start()
+        # Try to set up an SMTP test server.  In case other test runs are
+        # going on at the same time, try a range of ports.
+        base = ietf.utils.mail.SMTP_ADDR['port']
+        for offset in range(10):
+            try:
+                # remember the value so ietf.utils.mail.send_smtp() will use the same
+                ietf.utils.mail.SMTP_ADDR['port'] = base + offset 
+                self.smtpd_driver = SMTPTestServerDriver((ietf.utils.mail.SMTP_ADDR['ip4'],ietf.utils.mail.SMTP_ADDR['port']),None) 
+                self.smtpd_driver.start()
+                print("     Running an SMTP test server on %(ip4)s:%(port)s to catch outgoing email." % ietf.utils.mail.SMTP_ADDR)
+                break
+            except socket.error:
+                pass
+
 
         super(IetfTestRunner, self).setup_test_environment(**kwargs)