[manual] Rename Django app from zephyr to zerver.

This needs to be deployed to both staging and prod at the same
off-peak time (and the schema migration run).

At the time it is deployed, we need to make a few changes directly in
the database:

(1) UPDATE django_content_type set app_label='zerver' where app_label='zephyr';
(2) UPDATE south_migrationhistory set app_name='zerver' where app_name='zephyr';

(imported from commit eb3fd719571740189514ef0b884738cb30df1320)

zerver/management/commands/explain_js_error.py

@@ -0,0 +1,49 @@
+from __future__ import absolute_import
+
+import os
+import sys
+import select
+
+from django.core.management.base import BaseCommand, CommandError
+
+from zerver.lib.unminify import SourceMap
+
+# Wait for the user to paste text, then time out quickly and
+# return it.  Disable echo so that we can re-echo the same
+# lines with our annotations.
+def get_full_paste():
+    try:
+        os.system('stty -echo raw isig')
+
+        data = ''
+        while True:
+            fd = sys.stdin.fileno()
+            can_read = select.select([fd], [], [], 0.1)[0]
+            if can_read:
+                data += os.read(fd, 1)
+            else:
+                if data:
+                    return data
+    finally:
+        os.system('stty cooked echo')
+
+class Command(BaseCommand):
+    args = '<source map directory>'
+    help = '''Add source locations to a stack backtrace generated by minified code.
+
+The currently checked out code should match the version that generated the error.'''
+
+    def handle(self, *args, **options):
+        if len(args) != 1:
+            raise CommandError('No source map directory specified')
+
+        source_map = SourceMap(args[0])
+
+        if os.isatty(sys.stdin.fileno()):
+            sys.stdout.write('Paste stacktrace:\n\n')
+            sys.stdout.flush()
+            stacktrace = get_full_paste()
+        else:
+            stacktrace = sys.stdin.read()
+
+        sys.stdout.write(source_map.annotate_stacktrace(stacktrace))