Changed ca_errmsg callback to a more generic variant

Includes all error, log and debug messages
See [Customized NETCONF error message](https://github.com/clicon/clixon/issues/454)

test/test_cli_err.sh

@@ -0,0 +1,110 @@
+#!/usr/bin/env bash
+# Customixed error test
+
+# Magic line must be first in script (see README.md)
+s="$_" ; . ./lib.sh || if [ "$s" = $0 ]; then exit 0; else return 0; fi
+
+APPNAME=example
+
+# include err() and new() functions and creates $dir
+
+cfg=$dir/conf_yang.xml
+fyang=$dir/$APPNAME.yang
+clidir=$dir/cli
+if [ -d $clidir ]; then
+    rm -rf $clidir/*
+else
+    mkdir $clidir
+fi
+
+# Generate autocli for these modules
+AUTOCLI=$(autocli_config ${APPNAME} kw-all false)
+
+cat <<EOF > $cfg
+<clixon-config xmlns="http://clicon.org/config">
+  <CLICON_CONFIGFILE>$cfg</CLICON_CONFIGFILE>
+  <CLICON_YANG_DIR>${YANG_INSTALLDIR}</CLICON_YANG_DIR>
+  <CLICON_YANG_DIR>$dir</CLICON_YANG_DIR>
+  <CLICON_YANG_MAIN_FILE>$fyang</CLICON_YANG_MAIN_FILE>
+  <CLICON_CLISPEC_DIR>$clidir</CLICON_CLISPEC_DIR>
+  <CLICON_CLI_DIR>/usr/local/lib/$APPNAME/cli</CLICON_CLI_DIR>
+  <CLICON_CLI_MODE>$APPNAME</CLICON_CLI_MODE>
+  <CLICON_SOCK>/usr/local/var/run/$APPNAME.sock</CLICON_SOCK>
+  <CLICON_BACKEND_PIDFILE>/usr/local/var/run/$APPNAME.pidfile</CLICON_BACKEND_PIDFILE>
+  <CLICON_XMLDB_DIR>/usr/local/var/$APPNAME</CLICON_XMLDB_DIR>
+  ${AUTOCLI}
+</clixon-config>
+EOF
+
+cat <<EOF > $fyang
+module $APPNAME {
+  namespace "urn:example:m";
+  prefix m;
+  container x {
+    list m1 {
+      key "a b";
+      leaf a {
+        type string;
+      }
+      leaf b {
+        type string;
+      }
+      leaf c {
+        type string;
+      }
+    }
+  }
+}
+EOF
+
+cat <<EOF > $clidir/ex.cli
+CLICON_MODE="example";
+CLICON_PROMPT="%U@%H> ";
+CLICON_PLUGIN="example_cli";
+
+show config @datamodel, cli_show_auto("candidate", "cli");
+example("Example callback") {
+    <var:int32>("Just a random number"), mycallback("myarg");
+    error {
+      customized, myerror();     # Customized error message
+      orig, cli_remove(); # Original
+    }
+}
+
+
+EOF
+
+new "test params: -f $cfg"
+if [ $BE -ne 0 ]; then
+    new "kill old backend"
+    sudo clixon_backend -z -f $cfg
+    if [ $? -ne 0 ]; then
+        err
+    fi
+    new "start backend -s init -f $cfg"
+    start_backend -s init -f $cfg
+fi
+
+new "wait backend"
+wait_backend
+
+new "orig error"
+expectpart "$($clixon_cli -1 -f $cfg -l n example error orig)" 255 "Config error: api-path syntax error " ": application invalid-value Invalid api-path:  (must start with '/')"
+
+new "customized error"
+expectpart "$($clixon_cli -1 -f $cfg -l n example error custom)" 255 "My new err-string"
+
+if [ $BE -ne 0 ]; then
+    new "Kill backend"
+    # Check if premature kill
+    pid=$(pgrep -u root -f clixon_backend)
+    if [ -z "$pid" ]; then
+        err "backend already dead"
+    fi
+    # kill backend
+    stop_backend -f $cfg
+fi
+
+endtest
+
+rm -rf $dir