Quote the requirement otherwise it captures stdout.

docker/build/go-agent/Dockerfile

@@ -58,7 +58,7 @@ RUN \
 
 
 # Install AWS command-line interface - for AWS operations in a go-agent task.
-RUN pip install awscli>=1.11.58
+RUN pip install 'awscli>=1.11.58'
 
 # !!!!NOTICE!!!! ---- Runner of this pipeline take heed!! You must replace go_github_key.pem with the REAL key material
 # that can checkout private github repositories used as pipeline materials. The key material here is faked and is only