demo: generate CA cert automatically instead of providing 1 in repository

demo/ca.crt

------BEGIN CERTIFICATE-----
-MIIDTTCCAjWgAwIBAgIHASABDbgAQjANBgkqhkiG9w0BAQUFADA+MRowGAYDVQQD
-DBFyZTZzdC5leGFtcGxlLmNvbTEgMB4GCSqGSIb3DQEJARYRcmU2c3RAZXhhbXBs
-ZS5jb20wHhcNMTIwOTA2MTI0MTM0WhcNMjAwMTAxMTI0MTM0WjA+MRowGAYDVQQD
-DBFyZTZzdC5leGFtcGxlLmNvbTEgMB4GCSqGSIb3DQEJARYRcmU2c3RAZXhhbXBs
-ZS5jb20wggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQCzKdaI1gddt8iN
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-BHVSXzkQpVupxi86wEFIrkzlAYZRmY0fRcprhovI1iDLpdsJsY/yyPgfXNJk9xhT
-lPUoNxyH0EPhGv0KArJZkwlzdDj5RVYYcLTEge374gr1EIMyzex/kN5y1as2tX9l
-wXTROc5pAgMBAAGjUDBOMB0GA1UdDgQWBBSgDNnHOCF5xSGbmA9SCujCLRs0nTAf
-BgNVHSMEGDAWgBSgDNnHOCF5xSGbmA9SCujCLRs0nTAMBgNVHRMEBTADAQH/MA0G
-CSqGSIb3DQEBBQUAA4IBAQBZQvMkCSCrrJoS432kJUg//iB0+c1mftbYTez+wqHq
-NzEPnv5EWJtYsYvZUx6huNvrv5UR9S9MkGyH1u8kw3mW5lRKTPBC9NdAgywhsDES
-VTDx02EZhsKEA2VaxhirGyJEDSgXADQNZNtB0Mw+M8/tociZKOiih6gwJw3sYcDz
-9mTQFG44YG2nSmxEqP2m+32km0gvxLNIyoCnZN1x25dcRcJ5H9AbbIfSZxC02rqc
-Wy0HLmfa7ZPLYD5Qz/TuCXXRXxyy5AYasVsz2GdXDNXRwiEmYqfM69EDtwZqTPZj
-cfJdgSNqrysIXYE6SgBi6RUtOlmBubdxke4EZZ4ImdGo
------END CERTIFICATE-----

demo/demo

@@ -5,6 +5,7 @@ IPTABLES = 'iptables'
 SCREEN = 'screen'
 VERBOSE = 4
 REGISTRY='10.0.0.2'
+CA_DAYS = 1000
 
 #                       registry
 #                           |.2
@@ -154,6 +155,10 @@ gateway1.screen('miniupnpd -d -f miniupnpd.conf -P miniupnpd.pid -a 10.1.1.1'
                 ' -i %s' % g1_if_0_name)
 if 1:
     import sqlite3
+    os.path.exists('ca.crt') or subprocess.check_call(
+        "openssl req -nodes -new -x509 -key registry/ca.key -out ca.crt"
+        " -subj /CN=re6st.example.com/emailAddress=re6st@example.com"
+        " -set_serial 0x120010db80042 -days %u" % CA_DAYS, shell=True)
     db_path = 'registry/registry.db'
     registry.screen('../re6st-registry @registry/re6st-registry.conf --db %s'
         ' --mailhost %s -v%u' % (db_path, os.path.abspath('mbox'), VERBOSE))