anchor.diff:  To validate that PostGIS is installed and which version is running, run the command:
   
   ....
  -psql -U postgres -c "SELECT postgis_full_version();"
  +psql -h postgres-gis -U testuser -c "SELECT postgis_full_version();"
   ....
   
   You should expect to see output similar to:
  
positive.code: psql -h postgres-gis -U testuser postgres
  ....
  
  You can view the extensions that postgres-gis has enabled by running:
  ....
  psql -h postgres-gis -U testuser userdb -c '\dx'
  ....
  
negative.code: The container creates a default database called *userdb*, a default user called
  *testuser* and a default password of *password*.
  
  ==== Docker
  
  Create the container as follows:
  