revive: enable rule to check for unhandled errors

Enable the revive rule to ensure we check the return values of various
function calls. Put common printing functions in the skip list of the
check, because no-one ever checks the error of those. :-)

Signed-off-by: John Mulligan <jmulligan@redhat.com>

.revive.toml

@@ -42,3 +42,7 @@ warningCode = 0
   arguments = [7]
 [rule.function-result-limit]
   arguments = [3]
+
+[rule.unhandled-error]
+  # functions to ignore unhandled errors on
+  arguments = ["fmt.Printf", "fmt.Println"]