There is very rarely recevied error

return STDOUT {"error": {"class": "GenericError", "desc": "JSON parse error, invalid keyword 'execute'"}}
{"error": {"class": "GenericError", "desc": "Invalid JSON syntax"}}
{"error": {"class": "GenericError", "desc": "JSON parse error, invalid keyword 'guest'"}}
{"error": {"class": "GenericError", "desc": "Invalid JSON syntax"}}
{"error": {"class": "GenericError", "desc": "JSON parse error, invalid keyword 'ing'"}}

It is not possible to reproduce it but we recevied it third time in three weeks so we need to find the root cause. The last affected job (test log file attached):
https://jenkins.fd.io/view/vpp/job/vpp-csit-verify-virl/452/

Workaround is to run the test job again to allow vpp commit.