Throw more instructive errors when transfer responses aren't JSON

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@stellar/wallet-sdk",
-  "version": "0.0.8-rc.5",
+  "version": "0.0.8-rc.6",
   "description": "Libraries to help you write Stellar-enabled wallets in Javascript",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",

src/transfers/DepositProvider.ts

@@ -108,7 +108,15 @@ export class DepositProvider extends TransferProvider {
     const response = await fetch(`${this.transferServer}/deposit?${qs}`, {
       headers: isAuthRequired ? this.getHeaders() : undefined,
     });
-    const json = (await response.json()) as TransferResponse;
+
+    const text = await response.text();
+    let json;
+
+    try {
+      json = JSON.parse(text) as TransferResponse;
+    } catch (e) {
+      throw new Error(`Error parsing the deposit response as JSON: ${text}`);
+    }
 
     if (json.error) {
       const error: TransferError = new Error(

src/transfers/WithdrawProvider.ts

@@ -103,7 +103,15 @@ export class WithdrawProvider extends TransferProvider {
     const response = await fetch(`${this.transferServer}/withdraw?${qs}`, {
       headers: isAuthRequired ? this.getHeaders() : undefined,
     });
-    const json = (await response.json()) as TransferResponse;
+
+    const text = await response.text();
+    let json;
+
+    try {
+      json = JSON.parse(text) as TransferResponse;
+    } catch (e) {
+      throw new Error(`Error parsing the deposit response as JSON: ${text}`);
+    }
 
     if (json.error) {
       const error: TransferError = new Error(json.error);