[FEATURE] No way to get why a connection fails

[lmichel]

TapHandle cannot connect those 2 services

• http://taphandle.astro.unistra.fr/tapcomplex/app/Tap_Handle_MK2/taphandle.html?url=https://gaia.obspm.fr/tap-server/tap
• http://taphandle.astro.unistra.fr/tapcomplex/app/Tap_Handle_MK2/taphandle.html?url=http://voparis-tap-maser.obspm.fr:80/tap

No message on the screen or the console either helping to understand why.

[galyfray]

when trying to connect http://taphandle.astro.unistra.fr/tapcomplex/app/Tap_Handle_MK2/taphandle.html?url=https://gaia.obspm.fr/tap-server/tap a message appear on my screen and the logs dumps info about an error 400.
When looking in the network tab we see two errors :

• a CORS handled by the proxy
• a 400 with a voTable joined :

<?xml version="1.0" encoding="utf-8"?>
<VOTABLE version="1.3" xmlns="http://www.ivoa.net/xml/VOTable/v1.3" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.ivoa.net/xml/VOTable/v1.3 http://www.ivoa.net/xml/VOTable/v1.3">
<RESOURCE type="results">
<INFO name="QUERY_STATUS" value="ERROR">Incorrect ADQL query: 3 unresolved identifiers: schemas [l.1 c.76 - l.1 c.94], schema_name [l.1 c.8 - l.1 c.38], description [l.1 c.40 - l.1 c.70]!
 - Unknown table "tap_schema.schemas" !
 - Unknown column "tap_schema.schemas.schema_name" !
 - Unknown column "tap_schema.schemas.description" !</INFO>
<INFO  name="REQ_ID" value="S1642152747759"/>
<INFO  name="ERROR_TYPE" value="fatal"/>
<INFO  name="ACTION" value="sync"/>
</RESOURCE>
</VOTABLE>

And I am able to connect to http://taphandle.astro.unistra.fr/tapcomplex/app/Tap_Handle_MK2/taphandle.html?url=http://voparis-tap-maser.obspm.fr:80/tap without any trouble.