Inform in shell that env is active.

component/slapos/buildout.cfg

@@ -78,6 +78,7 @@ input = inline:
   export LDFLAGS="${environment:LDFLAGS}"
   export PKG_CONFIG_PATH="${environment:PKG_CONFIG_PATH}"
   export LD_LIBRARY_PATH="${environment:LD_LIBRARY_PATH}"
+  export PS1="[SlapOS env Active] $PS1"
 output = ${buildout:directory}/environment.sh
 
 [lxml-python]