Site rendering docker container fails to generate some parts of the site.

docker run -it --rm -p 4567:4567 -p 35729:35729 -v /Users/till/Development/mesos:/mesos  -v /Users/till/Development/mesos/site/publish:/mesos/site/publish     mesos/website

[...]
Creating destination directory: "source/api/latest/java/"
Loading source files for package org.apache.mesos...
Constructing Javadoc information...
../build/src/java/generated/org/apache/mesos/Protos.java:18678: error: package com.google.protobuf does not exist
      com.google.protobuf.GeneratedMessage implements
                         ^
../build/src/java/generated/org/apache/mesos/Protos.java:18376: error: package com.google.protobuf does not exist
      com.google.protobuf.MessageOrBuilder {
[...]
4283 warnings
Building website from static source
An error was encountered when generating the site
== The Middleman is loading