Error with Cassandra on Debian wheezy, what should I do?

Question

Debian

Hello. I've been fighting with Cassandra all night, I can't start it.
Every time I get the error
[FAIL] could not access pidfile for Cassandra ... failed!
Access must be given to some file, but which one?
How to fix this error?
Log of how I fought with all this scale:

Hit http://debian.mirror.cloudmouse.com wheezy Release.gpg
куча кода...
Ign http://ftp.ru.debian.org squeeze-updates/non-free Translation-en_US
Ign http://ftp.ru.debian.org squeeze-updates/non-free Translation-en
Hit http://nginx.org squeeze/nginx amd64 Packages
Ign http://nginx.org squeeze/nginx Translation-en_US
Ign http://nginx.org squeeze/nginx Translation-en
Fetched 20.0 kB in 2s (7,298 B/s)
Reading package lists... Done
W: GPG error: http://deb.rulezz.ru aml Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A7BD3FFFF8524CCA
W: GPG error: http://debian.datastax.com stable Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 350200F2B999A372
W: GPG error: http://nginx.org squeeze Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY ABF5BD827BD9BF62
[email protected]:/home/debian# sudo apt-get install cassandra
Reading package lists... Done
Building dependency tree
Reading state information... Done
cassandra is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 3 not upgraded.
[email protected]:/home/debian# /etc/init.d/cassandra start
[email protected]:/home/debian# bin/mg_procman
Traceback (most recent call last):
  File "bin/mg_procman", line 18, in <module>
    from mg.constructor.processes import ConstructorInstance
  File "/home/debian/mg/__init__.py", line 18, in <module>
    from mg.core.common import *
  File "/home/debian/mg/core/common.py", line 18, in <module>
    from mg.core.cass import CassandraObject, CassandraObjectList
  File "/home/debian/mg/core/cass.py", line 18, in <module>
    from concurrence.http import HTTPConnection, HTTPRequest
ImportError: No module named concurrence.http
[email protected]:/home/debian# service cassandra start
[email protected]:/home/debian#
[email protected]:/home/debian# service cassandra start
[email protected]:/home/debian# service cassandra status
[FAIL] could not access pidfile for Cassandra ... failed!
[email protected]:/home/debian# ^C
[email protected]:/home/debian#

There is no more (full) piece, because the server is not unlimited :)
I'm waiting for help.
The question itself:
1) What to do?
2) If you need to what file to raise the rights?