Quote illegal argv value, in error log.Fatalf.
Quote illegal argv value, in error log.Fatalf.

Print it as a string literal, so no escape sequences & weird stuff
will be sent to the error log output.

Example:

$ ./main test2.j foobar^G^A
2017/05/24 13:29:33 Error in jsonnet_main: Expected arg to be 'key=value': "foobar\a\x01"

mmikulicic/jsonnet_cgo,mmikulicic/jsonnet_cgo,mmikulicic/jsonnet_cgo,mmikulicic/jsonnet_cgo