Return errors as JSON rather than HTML
Return errors as JSON rather than HTML


Former-commit-id: f46f107f62f1527f1e3c0c479a7c8bbe54c8db89
robbrockbank/libcalico,projectcalico/libnetwork-plugin,TrimBiggs/libnetwork-plugin,L-MA/libcalico,plwhite/libcalico,insequent/libcalico,alexhersh/libcalico,caseydavenport/libcalico,projectcalico/libcalico,tomdee/libcalico,TrimBiggs/libcalico,TrimBiggs/libnetwork-plugin,djosborne/libcalico,tomdee/libnetwork-plugin,Symmetric/libcalico