gnc-fq-dump: Err msg if AlphaVantage API Key is needed but missing

AlphaVantage API Key is needed for all currency quotes
and stock quotes with source 'alphavantage' or 'vanguard' or
multi sources that include 'alphavantage'

libgnucash/quotes/gnc-fq-dump.in

@@ -141,6 +141,25 @@ sub report {
   }
 }
 
+sub chk_api_key {
+  my $exch = $_[0];
+  my $url = " https://wiki.gnucash.org/wiki/Online_Quotes#Source_Alphavantage.2C_US\n";
+  if (($exch eq "currency") || ($exch eq "alphavantage")
+  ||  ($exch eq "vanguard")) {
+    die "ERROR: ALPHAVANTAGE_API_KEY *must* be set for currency quotes and \n" .
+        " stock quotes with source 'alphavantage' or 'vanguard'; see\n" . $url
+      unless (defined ($ENV{'ALPHAVANTAGE_API_KEY'}));
+  }
+  if (($exch eq "canada") || ($exch eq "nasdaq")
+  ||  ($exch eq "nyse")   || ($exch eq "usa")) {
+    printf("WARNING: Multiple Source '%s' will not be able to use alphavantage " .
+        "unless ALPHAVANTAGE_API_KEY is set; see\n%s", $exch, $url)
+      unless (defined ($ENV{'ALPHAVANTAGE_API_KEY'}));
+    }
+}
+
+############## end of functions - start mainline #########################
+
 # Check for and load non-standard modules
 check_modules ();
 
@@ -162,6 +181,7 @@ if ($ARGV[0] eq "-v") {
 }
 
 my $exchange = shift;
+chk_api_key ($exchange);
 if ($exchange eq "currency") {
   my $from = shift;
   while ($#ARGV >= 0) {