Issue #25940: Use self-signed.pythontest.net in SSL tests

This is instead of svn.python.org, whose certificate recently expired, and
whose new certificate uses a different root certificate.

The certificate used at the pythontest server was modifed to set the "basic
constraints" CA flag. This flag seems to be required for test_get_ca_certs_
capath() to work.

Added the new self-signed certificate to capath with the following commands:

cp Lib/test/{selfsigned_pythontestdotnet.pem,capath/}
c_rehash -v Lib/test/capath/
c_rehash -v -old Lib/test/capath/
# Note the generated file names
cp Lib/test/capath/{selfsigned_pythontestdotnet.pem,0e4015b9.0}
mv Lib/test/capath/{selfsigned_pythontestdotnet.pem,ce7b8643.0}

When attempting to connect to port 444 on the new server, the resulting error
code is EHOSTUNREACH on Linux, and ETIMEDOUT on Windows.
diff --git a/Lib/test/selfsigned_pythontestdotnet.pem b/Lib/test/selfsigned_pythontestdotnet.pem
index 9a80073..b6d259b 100644
--- a/Lib/test/selfsigned_pythontestdotnet.pem
+++ b/Lib/test/selfsigned_pythontestdotnet.pem
@@ -1,5 +1,5 @@
 -----BEGIN CERTIFICATE-----
-MIIChzCCAfCgAwIBAgIJAKGU95wKR8pSMA0GCSqGSIb3DQEBBQUAMHAxCzAJBgNV
+MIIClTCCAf6gAwIBAgIJAKGU95wKR8pTMA0GCSqGSIb3DQEBBQUAMHAxCzAJBgNV
 BAYTAlhZMRcwFQYDVQQHDA5DYXN0bGUgQW50aHJheDEjMCEGA1UECgwaUHl0aG9u
 IFNvZnR3YXJlIEZvdW5kYXRpb24xIzAhBgNVBAMMGnNlbGYtc2lnbmVkLnB5dGhv
 bnRlc3QubmV0MB4XDTE0MTEwMjE4MDkyOVoXDTI0MTAzMDE4MDkyOVowcDELMAkG
@@ -8,9 +8,9 @@
 aG9udGVzdC5uZXQwgZ8wDQYJKoZIhvcNAQEBBQADgY0AMIGJAoGBANDXQXW9tjyZ
 Xt0Iv2tLL1+jinr4wGg36ioLDLFkMf+2Y1GL0v0BnKYG4N1OKlAU15LXGeGer8vm
 Sv/yIvmdrELvhAbbo3w4a9TMYQA4XkIVLdvu3mvNOAet+8PMJxn26dbDhG809ALv
-EHY57lQsBS3G59RZyBPVqAqmImWNJnVzAgMBAAGjKTAnMCUGA1UdEQQeMByCGnNl
-bGYtc2lnbmVkLnB5dGhvbnRlc3QubmV0MA0GCSqGSIb3DQEBBQUAA4GBAIOXmdtM
-eG9qzP9TiXW/Gc/zI4cBfdCpC+Y4gOfC9bQUC7hefix4iO3+iZjgy3X/FaRxUUoV
-HKiXcXIaWqTSUWp45cSh0MbwZXudp6JIAptzdAhvvCrPKeC9i9GvxsPD4LtDAL97
-vSaxQBezA7hdxZd90/EeyMgVZgAnTCnvAWX9
+EHY57lQsBS3G59RZyBPVqAqmImWNJnVzAgMBAAGjNzA1MCUGA1UdEQQeMByCGnNl
+bGYtc2lnbmVkLnB5dGhvbnRlc3QubmV0MAwGA1UdEwQFMAMBAf8wDQYJKoZIhvcN
+AQEFBQADgYEAIuzAhgMouJpNdf3URCHIineyoSt6WK/9+eyUcjlKOrDoXNZaD72h
+TXMeKYoWvJyVcSLKL8ckPtDobgP2OTt0UkyAaj0n+ZHaqq1lH2yVfGUA1ILJv515
+C8BqbvVZuqm3i7ygmw3bqE/lYMgOrYtXXnqOrz6nvsE6Yc9V9rFflOM=
 -----END CERTIFICATE-----