fix: check if `devil` command exists, as requested by @Neilpang

deploy/mydevil.sh

@@ -27,6 +27,11 @@ mydevil_deploy() {
   _debug _cca "$_cca"
   _debug _cfullchain "$_cfullchain"
 
+  if ! _exists "devil" ; then
+    _err "Could not find 'devil' command."
+    return 1
+  fi
+
   ip=$(mydevil_get_ip "$_cdomain")
   if [ -z "$ip" ]; then
     _err "Could not find IP for domain $_cdomain."

dnsapi/dns_mydevil.sh

@@ -18,6 +18,11 @@ dns_mydevil_add() {
   txtvalue=$2
   domain=""
 
+  if ! _exists "devil" ; then
+    _err "Could not find 'devil' command."
+    return 1
+  fi
+
   _info "Using mydevil"
 
   domain=$(mydevil_get_domain "$fulldomain")
@@ -48,6 +53,11 @@ dns_mydevil_rm() {
   txtvalue=$2
   domain=""
 
+  if ! _exists "devil" ; then
+    _err "Could not find 'devil' command."
+    return 1
+  fi
+
   _info "Using mydevil"
 
   domain=$(mydevil_get_domain "$fulldomain")