gcloud app deploy returns code: 13

[EnderAyalp]

I have the following problem:

When I run gcloud app deploy

I get the following error:

My app.yaml looks like this:

runtime: java
env: flex
And  my pom.xml, I have the following plugin:

<build> <plugins> <plugin> <groupId>com.google.cloud.tools</groupId> <artifactId>appengine-maven-plugin</artifactId> <version>2.4.4</version> <configuration> <version>1</version> <projectId>speechless-backend</projectId> </configuration> </plugin> 

please help