improved error messages for nonexisting or nonreadable files

dbLoadTemplate

@@ -107,6 +107,8 @@ sub parseSubst {
         $@ =~ /end of file/ or die $@;
         return 0;
     }
+    die "template file $filename not found in $ARGV line $.\n" unless -e $filename;
+    die "template file $filename not readable in $ARGV line $.\n" unless -r $filename;
     eval { expect "{","pattern|{ 'pattern' or '{'" };
     if ($_ eq "{") {
         # old style substitution
@@ -152,6 +154,10 @@ sub parseSubst {
 }
 
 sub parseFiles {
+    foreach (@_) {
+        die "file $_ not found.\n" unless -e $_;
+        die "file $_ not readable.\n" unless -r $_;
+    }
     foreach (@_) {
         local *ARGV;
         local %subst;