To regenerate certificates

1. Apply:

diff --git a/tools/wptserve/wptserve/sslutils/openssl.py b/tools/wptserve/wptserve/sslutils/openssl.py
index 87a8cc9cc7..bbf500d8ca 100644
--- a/tools/wptserve/wptserve/sslutils/openssl.py
+++ b/tools/wptserve/wptserve/sslutils/openssl.py
@@ -216,7 +216,7 @@ basicConstraints = CA:true
 subjectKeyIdentifier=hash
 authorityKeyIdentifier=keyid:always,issuer:always
 keyUsage = keyCertSign
-%(constraints_line)s
+#%(constraints_line)s
 """ % {"root_dir": root_dir,
        "san_line": san_line,
        "duration": duration,

1. cd test_util/wpt/
2. ./wpt serve --config tools/certs/config.json
3. Run:

cp test_util/wpt/tools/certs/cacert.key tools/wpt/certs/cacert.key
cp test_util/wpt/tools/certs/cacert.pem tools/wpt/certs/cacert.pem
cp test_util/wpt/tools/certs/web-platform.test.key tools/wpt/certs/web-platform.test.key
cp test_util/wpt/tools/certs/web-platform.test.pem tools/wpt/certs/web-platform.test.pem