Errors should not should "Error: " twice for an error message.

Using the command line:
office-addin-manifest modify test\manifests\manifest.xml

The output was appearing as:
Error: Error: You need to specify something to change in the manifest.

Fixed so the output appears as:
Error: You need to specify something to change in the manifest.

Author: akrantz

packages/office-addin-manifest/src/commands.ts

@@ -9,10 +9,14 @@ export async function info(manifestPath: string) {
     const manifest = await manifestInfo.readManifestFile(manifestPath);
     logManifestInfo(manifestPath, manifest);
   } catch (err) {
-    console.error(`Error: ${err}`);
+    logErrorMessage(err);
   }
 }
 
+function logErrorMessage(err: any) {
+  console.error(`Error: ${err instanceof Error ? err.message : err}`);
+}
+
 function logManifestInfo(manifestPath: string, manifest: manifestInfo.ManifestInfo) {
   console.log(`Manifest: ${manifestPath}`);
   console.log(`  Id: ${manifest.id || ""}`);
@@ -36,6 +40,6 @@ export async function modify(manifestPath: string, command: commnder.Command) {
     const manifest = await manifestInfo.modifyManifestFile(manifestPath, guid, displayName);
     logManifestInfo(manifestPath, manifest);
   } catch (err) {
-    console.error(`Error: ${err}`);
+    logErrorMessage(err);
   }
 }