Test: Get the smtp test server using os.getenv() (#117979)

The smtp test server can be set via CPYTHON_TEST_SMTP_SERVER environment variable.
If not set, it uses the default value smtp.gmail.com
This is needed because the network I'm on filters access to
smtp.gmail.com resulting in a failing test.

Co-authored-by: Łukasz Langa <[email protected]>

Author: diegorusso

Lib/test/test_smtpnet.py

@@ -2,13 +2,16 @@
 from test import support
 from test.support import import_helper
 from test.support import socket_helper
+import os
 import smtplib
 import socket
 
 ssl = import_helper.import_module("ssl")
 
 support.requires("network")
 
+SMTP_TEST_SERVER = os.getenv('CPYTHON_TEST_SMTP_SERVER', 'smtp.gmail.com')
+
 def check_ssl_verifiy(host, port):
     context = ssl.create_default_context()
     with socket.create_connection((host, port)) as sock:
@@ -22,7 +25,7 @@ def check_ssl_verifiy(host, port):
 
 
 class SmtpTest(unittest.TestCase):
-    testServer = 'smtp.gmail.com'
+    testServer = SMTP_TEST_SERVER
     remotePort = 587
 
     def test_connect_starttls(self):
@@ -44,7 +47,7 @@ def test_connect_starttls(self):
 
 
 class SmtpSSLTest(unittest.TestCase):
-    testServer = 'smtp.gmail.com'
+    testServer = SMTP_TEST_SERVER
     remotePort = 465
 
     def test_connect(self):