[GNC] Online quotes not working for currency rates (Perl library works)

[Chang Wang]

Hi,
I'm having trouble getting the quotes of currency exchange rates using
Finance::Quote.

The situation:

* I can get quotes successfully for stocks using "Get Quotes" in the
price database. But not the currency I'm using.

* I'm on MacOS.
```
ALPHAVANTAGE_API_KEY=XXX
/Applications/Gnucash.app/Contents/MacOS/gnucash-cli --quotes dump
currency USD JPY
```
gives
```
JPY Finance::Quote returned no data and set no error.
```
The same error message also appears in GUI (I have entered the API key
in the preferences).

However, if I write a Perl script that directly calls Finance::Quote
with my API key, I can get the USDJPY rate successfully.

* I'm also unable to change the quote source of currency rates from
the security editor. The default is "Single - currency." When I change
it to something else and hit OK, next time I open it, the source is
reverted back to single.

I think this might be caused by GnuCash itself? Any hint on how I can
circumvent this problem? Thanks!

Best,
Chang