Ammonia cannot be dried over anhydrous calcium chloride. why?

When water is absorbed by calcium chloride, it undergoes hydrolysis to give hydrochloric acid 
${\mathrm{CaCl}}_2+2{\mathrm{H}}_2\mathrm{O} \to \mathrm{Ca}{\left(\mathrm{OH}\right)}_{2 }+ 2 \mathrm{Hcl}$
Since ammonia is basic, it is neutralized by HCI to give salt, Hence ammonia is dried over a basic oxide, quick lime.