casper: Fix issues with server autoreloading on save.

This fixes an issue where if you saved a Python file (even just
changing whitespace) while casper tests were running, the Tornado
server being used would restart, triggering a confusing error like
this:

ReferenceError: Can't find variable: $
Traceback:
  undefined:2
  :4
Suite explicitly interrupted without any message given.

tools/run-dev.py

@@ -96,10 +96,13 @@ if options.interface is None:
 elif options.interface == "":
     options.interface = None
 
+runserver_args = []
 base_port = 9991
 if options.test:
     base_port = 9981
     settings_module = "zproject.test_settings"
+    # Don't auto-reload when running casper tests
+    runserver_args = ['--noreload']
 else:
     settings_module = "zproject.settings"
 
@@ -154,7 +157,7 @@ pid_file.close()
 # zulip/urls.py.
 cmds = [['./tools/compile-handlebars-templates', 'forever'],
         ['./manage.py', 'runserver'] +
-        manage_args + ['127.0.0.1:%d' % (django_port,)],
+        manage_args + runserver_args + ['127.0.0.1:%d' % (django_port,)],
         ['env', 'PYTHONUNBUFFERED=1', './manage.py', 'runtornado'] +
         manage_args + ['127.0.0.1:%d' % (tornado_port,)],
         ['./tools/run-dev-queue-processors'] + manage_args,

zerver/tornado/application.py

@@ -19,5 +19,6 @@ def create_tornado_application():
     return tornado.web.Application(([(url, AsyncDjangoHandler) for url in urls] +
                                     get_sockjs_router().urls),
                                    debug=settings.DEBUG,
+                                   autoreload=settings.AUTORELOAD,
                                    # Disable Tornado's own request logging, since we have our own
                                    log_function=lambda x: None)

zproject/settings.py

@@ -363,6 +363,7 @@ ZILENCER_ENABLED = 'zilencer' in INSTALLED_APPS
 # We override the port number when running frontend tests.
 TORNADO_SERVER = 'http://127.0.0.1:9993'
 RUNNING_INSIDE_TORNADO = False
+AUTORELOAD = DEBUG
 
 ########################################################################
 # DATABASE CONFIGURATION

zproject/test_settings.py

@@ -96,8 +96,12 @@ CACHES['database'] = {
     }
 }
 
-# Use local memory cache for backend tests.
-if not CASPER_TESTS:
+
+if CASPER_TESTS:
+    # Don't auto-restart Tornado server during casper tests
+    AUTORELOAD = False
+else:
+    # Use local memory cache for backend tests.
     CACHES['default'] = {
         'BACKEND': 'django.core.cache.backends.locmem.LocMemCache'
     }