Workaround to virtual environment's nounset bug.

Workaround to pypa/virtualenv#150

run-build-server.sh

@@ -7,18 +7,20 @@ err_handler() {
 
 trap 'err_handler $LINENO' ERR
 
-# Fail fast (err_handler above will be invoked)
-# Exit immediately if a command exits with a non-zero status.
-set -o errexit
-# Treat unset variables as an error when substituting.
-set -o nounset
-
 # cd to the scripts current directory
 cd -P -- "$(dirname -- "$0")"
 
+# As a workaround to https://github.com/pypa/virtualenv/issues/150 , we should 
+# enable the virtual environment before setting "nounset"
 echo "Enabling virtual environment"
 source env/bin/activate
 
+# Fail fast (err_handler above will be invoked)
+# Exit immediately if a command exits with a non-zero status.
+set -o errexit
+# Treat unset variables as an error when substituting.
+set -o nounset
+
 # TODO: Load variables in a more modular way
 echo "Sourcing environment variables"
 . workers/static-config.sh