even closer to real docker compose command

After more thorough investigation, tried to reproduced a closer behaviour to native docker compose CLI

lib/networks.js

@@ -46,12 +46,21 @@ async function up(docker, projectName, recipe, output) {
       continue;
     }
     if (network.external === true) {
-      let returnedNetwork = await docker.listNetworks({
-        filters: { name: [ network.name || networkName ] },
+      const networkLookupName = network.name || networkName;
+
+      let returnedNetworks = await docker.listNetworks({
+        filters: { name: [ networkLookupName ] },
       });
+
+      const externalNetwork = returnedNetworks.find(network => network.Name === networkLookupName)
+
+      if(!externalNetwork){
+        throw new Error(`network ${networkLookupName} declared as external, but could not be found`)
+      }
+
       networks.push({
         name: projectName + '_' + networkName,
-        network: await docker.getNetwork(returnedNetwork[0].Id),
+        network: await docker.getNetwork(externalNetwork.Id),
       });
       continue;
     }