Fixing dpkg / apt-get Problem With Python2.6

While trying to upgrade to Python 2.6 on one of my development machines tonight I was faced by an error message after running apt-get install python2.6:

After unpacking 0B of additional disk space will be used.
Setting up python2.6-minimal (2.6.4-4) ...
Linking and byte-compiling packages for runtime python2.6...
pycentral: pycentral rtinstall: installed runtime python2.6 not found
pycentral rtinstall: installed runtime python2.6 not found
dpkg: error processing python2.6-minimal (--configure):
 subprocess post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of python2.6:
 python2.6 depends on python2.6-minimal (= 2.6.4-4); however:
  Package python2.6-minimal is not configured yet.
dpkg: error processing python2.6 (--configure):
 dependency problems - leaving unconfigured
Errors were encountered while processing:
E: Sub-process /usr/bin/dpkg returned an error code (1)

Attempting to install python2.6-minimal wouldn’t work, attempting to install python2.6 proved to have the same problem.

Luckily the Launchpad thread for python-central provided the answer: Upgrade python-central first!

:~# apt-get install python-central
Setting up python2.6 (2.6.4-4) ...
Setting up python-central (0.6.14+nmu2) ...

Fatal error: Undefined class constant ‘ATTR_DEFAULT_FETCH_MODE’

This is one of the common error messages that seems to appear after installing PHP – in particular under Ubuntu or Debian (where I experienced it). The reason for this is that the PDO version you’ve just installed is too old for the constant to exist, usually because you where naive enough to install the extension from PECL instead of using the default supplied by ubuntu. If you did the same as me:

apt-get install 
pecl install pdo
pecl install pdo_mysql

/etc/init.d/apache2 restart

And everything seems to work, except for that missing constant. What the fsck?!

The reason is that the PECL version of PDO is no longer maintained (I’d suggest to automagically push the newest version to PECL too, just so pecl install and pecl upgrade works as expected). The fact is that when you did pecl install pdo, you destroyed the more recent version provided by the default php5-common package (under Ubuntu, at least).

To solve the problem (and if you also did pecl install pdo_mysql, you’ll have to replace that one too…)

apt-get install --reinstall php5-common php5-mysql php5-mysqli

Restart. Relive. Re.. eh .. yeah. Rerere.

If you’re building from source, you’ll need to add:

--enable-pdo --with-pdo-mysql --with-pdo-pgsql (and any other driver you need)