Hello,
The error you mentioned,
indicates that there may be resources you are using that may be dependent on Google App Engine. The first step is to know what resources are in your pipeline that are being built. From the information you provided, I have not found any common issue at this time that may cause
the error you reported. So this is why I am leaning towards the resources of the build process. The best way to move forward, since Google Groups is meant for general discussions, is to open a thread on
Stackoverflow in order to go through your build process and to isolate the
cause.
This way, you may get the help of the programming community to further diagnose the build steps. I am unable to provide a fix now because there is no sufficient information about your build steps.