Fix error when STUDIO_NAME uses non-ascii characters

The replacement strings need to be unicode, so that when STUDIO_NAME contains non-ascii characters python can handle it correctly without raising exceptions.
Also, the value of STUDIO_SHORT_NAME can be read from cms.env.json.

cms/envs/aws.py

@@ -199,6 +199,7 @@ LOGGING = get_logger_config(LOG_DIR,
 #theming start:
 PLATFORM_NAME = ENV_TOKENS.get('PLATFORM_NAME', 'edX')
 STUDIO_NAME = ENV_TOKENS.get('STUDIO_NAME', 'edX Studio')
+STUDIO_SHORT_NAME = ENV_TOKENS.get('STUDIO_SHORT_NAME', 'Studio')
 TENDER_DOMAIN = ENV_TOKENS.get('TENDER_DOMAIN', TENDER_DOMAIN)
 TENDER_SUBDOMAIN = ENV_TOKENS.get('TENDER_SUBDOMAIN', TENDER_SUBDOMAIN)
 

cms/templates/500.html

@@ -9,7 +9,7 @@
     <header>
       <h1 class="title title-1">
         ${_("The {studio_name} servers encountered an error").format(
-          studio_name="<em>{studio_name}</em>".format(studio_name=settings.STUDIO_SHORT_NAME)
+          studio_name=u"<em>{studio_name}</em>".format(studio_name=settings.STUDIO_SHORT_NAME)
         )}
       </h1>
     </header>

cms/templates/howitworks.html

@@ -16,7 +16,7 @@
     <header>
       ## "edX Studio" should not be translated
       <h1><span class="wrapper-text-welcome">${_("Welcome to {studio_name}").format(
-        studio_name='</span><span class="logo">{studio_name}</span>'.format(
+        studio_name=u'</span><span class="logo">{studio_name}</span>'.format(
           studio_name=settings.STUDIO_NAME
         )
       )}</h1>