handle error from blockexplores

lib/server.js

@@ -458,7 +458,7 @@ WalletService.prototype._getUtxos = function(cb) {
 
     var bc = self._getBlockchainExplorer('insight', networkName);
     bc.getUnspentUtxos(addressStrs, function(err, inutxos) {
-      if (err) return cb(err);
+      if (err) return cb(new Error('Could not fetch unspend outputs:' + err));
       var utxos = _.map(inutxos, function(i) {
         return _.pick(i.toObject(), ['txid', 'vout', 'address', 'scriptPubKey', 'amount', 'satoshis']);
       });
@@ -1121,7 +1121,7 @@ WalletService.prototype.getTxHistory = function(opts, cb) {
       },
       function(next) {
         bc.getTransactions(addressStrs, null, null, function(err, txs) {
-          if (err) return next(err);
+          if (err) return next('Could not fetch transactions: ' + err);
 
           next(null, self._normalizeTxHistory(txs));
         });
@@ -1179,7 +1179,7 @@ WalletService.prototype.scan = function(opts, cb) {
         if (err) return next(err);
         allAddresses.push(addresses);
         checkActivity(_.pluck(addresses, 'address'), function(err, thereIsActivity) {
-          if (err) return next(err);
+          if (err) return next('Could not fetch TX activity:' + err);
           activity = thereIsActivity;
           next();
         });