chore: work around lack of USDC PSM

packages/fast-usdc/src/fast-usdc.start.js

@@ -72,6 +72,28 @@ const publishDisplayInfo = async (brand, { board, chainStorage }) => {
   await E(node).setValue(JSON.stringify(aux));
 };
 
+/**
+ * Look up USDC issuer. Since it's not available in some test
+ * contexts, use USDC_axl as a fall-back.
+ *
+ * UNTIL https://github.com/Agoric/agoric-3-proposals/issues/19
+ * @param {BootstrapPowers['consume']['agoricNames']} agoricNames
+ */
+const lookupUSDCIssuer = async agoricNames => {
+  await null;
+  try {
+    /** @type {Issuer<'nat'>} */
+    const issuer = await E(agoricNames).lookup('issuer', 'USDC');
+    return issuer;
+  } catch (notFound) {
+    console.warn('USDC not found; using USDC_axl fallback', notFound);
+
+    /** @type {Issuer<'nat'>} */
+    const issuer = await E(agoricNames).lookup('issuer', 'USDC_axl');
+    return issuer;
+  }
+};
+
 /**
  * @typedef { PromiseSpaceOf<{
  *   fastUsdcKit: FastUSDCKit
@@ -125,8 +147,7 @@ export const startFastUSDC = async (
   trace('startFastUSDC');
 
   await null;
-  /** @type {Issuer<'nat'>} */
-  const USDCissuer = await E(agoricNames).lookup('issuer', 'USDC');
+  const USDCissuer = await lookupUSDCIssuer(agoricNames);
   const brands = harden({
     USDC: await E(USDCissuer).getBrand(),
   });