Give a good error message when student has already registered with their email address

[rcmiller]

Traceback (most recent call last):

File "/usr/lib/python2.7/site-packages/django/core/handlers/base.py", line 111, in get_response response = callback(request, _callback_args, *_callback_kwargs)

File "/usr/lib/python2.7/site-packages/django/contrib/auth/decorators.py", line 20, in _wrapped_view return view_func(request, _args, *_kwargs)

File "/mit/eecs/Scripts/django/coursemgmt/views.py", line 3311, in staff_register st.save()

File "/usr/lib/python2.7/site-packages/django/db/models/base.py", line 463, in save self.save_base(using=using, force_insert=force_insert, force_update=force_update)

File "/usr/lib/python2.7/site-packages/django/db/models/base.py", line 551, in save_base result = manager._insert([self], fields=fields, return_id=update_pk, using=using, raw=raw)

File "/usr/lib/python2.7/site-packages/django/db/models/manager.py", line 203, in _insert return insert_query(self.model, objs, fields, **kwargs)

File "/usr/lib/python2.7/site-packages/django/db/models/query.py", line 1593, in insert_query return query.get_compiler(using=using).execute_sql(return_id)

File "/usr/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 912, in execute_sql cursor.execute(sql, params)

File "/usr/lib/python2.7/site-packages/django/db/backends/mysql/base.py", line 114, in execute return self.cursor.execute(query, args)

File "/usr/lib64/python2.7/site-packages/MySQLdb/cursors.py", line 174, in execute self.errorhandler(self, exc, value)

File "/usr/lib64/python2.7/site-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler raise errorclass, errorvalue

IntegrityError: (1062, "Duplicate entry 'abari@mit.edu' for key 'email'")