Make suggestions to the user when fetching fails

Specifically, trying to make typos and unauthenticated errors more
obvious to users beyond the API error response stating that the build
was not found.

Test: relocate `.acloud_oauth2.dat` file
Test: attempt to fetch an internal branch with no credential flags
Bug: 427744621

Author: cjreynol

base/cvd/cuttlefish/host/libs/web/android_build_api.cpp

@@ -227,9 +227,28 @@ Result<std::string> AndroidBuildApi::BuildStatus(const DeviceBuild& build) {
       android_build_url_->GetBuildStatusUrl(build.id, build.target);
   auto response =
       CF_EXPECT(HttpGetToJson(http_client, url, CF_EXPECT(Headers())));
-  const Json::Value json = CF_EXPECT(GetResponseJson(response),
-                                     "Error fetching build status for build:\n"
-                                         << build);
+
+  std::string no_auth_error_message;
+  if (credential_source == nullptr && response.http_code == 404) {
+    // In LatestBuildId we currently cannot distinguish between the cases:
+    //    - user provided a build ID (not an error)
+    //    - user provided a branch with a typo
+    //    - user provided a branch without the necessary authentication
+    //    (for example, internal branches)
+    // This message is a best attempt at helping the user in third case
+    no_auth_error_message =
+        "\n\nThis fetch was run unauthenticated, which could be the "
+        "problem.\nTry `cvd help login`";
+  }
+  const Json::Value json = CF_EXPECT(
+      GetResponseJson(response),
+      "Error fetching build status for build:\n"
+          << build
+          << "\n\nIf you specified a branch and it appears in the build id "
+             "field of this error, there was a problem retrieving the latest "
+             "build id.\n\nIs there a typo in the branch or target name?"
+          << no_auth_error_message);
+
   return CF_EXPECT(GetValue<std::string>(json, { "buildAttemptStatus" }));
 }