Use retry_with_error in GCECredentials#fetch_access_token

lib/googleauth/compute_engine.rb

@@ -88,6 +88,8 @@ END
       def fetch_access_token(options = {})
         c = options[:connection] || Faraday.default_connection
         c.headers = { 'Metadata-Flavor' => 'Google' }
+
+        retry_with_error do
           resp = c.get(COMPUTE_AUTH_TOKEN_URI)
           case resp.status
           when 200
@@ -103,3 +105,4 @@ END
       end
     end
   end
+end

spec/googleauth/compute_engine_spec.rb

@@ -77,6 +77,20 @@ describe Google::Auth::GCECredentials do
           .to raise_error Signet::AuthorizationError
         expect(stub).to have_been_requested
       end
+
+      it 'should fail with Signet::AuthorizationError if request times out' do
+        allow_any_instance_of(Faraday::Connection).to receive(:get)
+          .and_raise(Faraday::TimeoutError)
+        expect { @client.fetch_access_token! }
+          .to raise_error Signet::AuthorizationError
+      end
+
+      it 'should fail with Signet::AuthorizationError if request fails' do
+        allow_any_instance_of(Faraday::Connection).to receive(:get)
+          .and_raise(Faraday::ConnectionFailed, nil)
+        expect { @client.fetch_access_token! }
+          .to raise_error Signet::AuthorizationError
+      end
     end
   end