==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 0.9.9
- Deployed with iRedMail Easy or the downloadable installer?
- Linux/BSD distribution name and version: CentOS 6.8
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP
- Web server (Apache or Nginx): NGINX
- Manage mail accounts with iRedAdmin-Pro? Yes
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

I use "Export all managed accounts" from panel. I get internal server error. iRedAdmin-Pro/mlmmjadmin restarted without luck, I get error in logs:

Traceback (most recent call last):#012  File "/usr/lib/python2.6/site-packages/web/application.py", line 239, in process#012    return self.handle()#012  File "/usr/lib/python2.6/site-packages/web/application.py", line 230, in handle#012    return self._delegate(fn, self.fvars, args)#012  File "/usr/lib/python2.6/site-packages/web/application.py", line 420, in _delegate#012    return handle_class(cls)#012  File "/usr/lib/python2.6/site-packages/web/application.py", line 396, in handle_class#012    return tocall(*args)#012  File "/var/www/iRedAdmin-Pro-LDAP-4.0/controllers/decorators.py", line 44, in proxyfunc#012    return func(self, *args, **kw)#012  File "/var/www/iRedAdmin-Pro-LDAP-4.0/controllers/ldap/export.py", line 70, in GET#012    with zipfile.ZipFile(f, mode='w', compression=zipfile.ZIP_DEFLATED) as zf:#012AttributeError: ZipFile instance has no attribute '__exit__'