chapter9: typo possibly

Moving ... is chance to rehearse the fiddliness
->
Moving ... is a chance to rehearse the fiddliness
             ^^

Author: zipperer

chapter_09_docker.asciidoc

@@ -1485,7 +1485,7 @@ Tests and small steps take some of the uncertainty out of deployment::
 
 Some typical pain points--networking, ports, static files, and the database::
     Moving from the local django development server to a container
-    is chance to rehearse the fiddliness of configuring networking
+    is a chance to rehearse the fiddliness of configuring networking
     in a deployed environment.
     It's also a chance to think about persistence and the database,
     and some configuration issues like static files.