fix dotdeb squeeze wheezy update error

After attempting a few server upgrades we started to see the following on a few machines that used the Dotdeb repositories:

server:~# apt-get upgrade -u
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages have been kept back:
  libapache2-mod-php5 php-pear php5 php5-apc php5-cgi php5-cli php5-common php5-curl php5-gd php5-mcrypt php5-memcache php5-mysql
0 upgraded, 0 newly installed, 0 to remove and 12 not upgraded.

After a quick check it was discovered the dotdeb have changed the repository call for stable and squeeze given the recent Debian 7.0 (wheezy) release. To fix this edit and change the sources.list file and replace "stable" with "oldstable" as such:

nano /etc/apt/sources.list

# change any dotdeb references to "oldstable"
deb http://packages.dotdeb.org oldstable all
deb-src http://packages.dotdeb.org oldstable all

Now you can run the usual update mechanism followed by an upgrade like so:

apt-get update
apt-get upgrade -u