To resolve I've included the dependency channel:
servidor@ubuntu$ sudo pecl channel-discover components.ez.no
Adding Channel "components.ez.no" succeeded
Discovery of channel "components.ez.no" succeeded
And then I installed Skeleton:
servidor@ubuntu$ sudo pear install --alldeps phpunit/PHPUnit_SkeletonGenerator
downloading PHPUnit_SkeletonGenerator-1.2.1.tgz ...
Starting to download PHPUnit_SkeletonGenerator-1.2.1.tgz (11,376 bytes)
.....done: 11,376 bytes
downloading ConsoleTools-1.6.1.tgz ...
Starting to download ConsoleTools-1.6.1.tgz (869,994 bytes)
...done: 869,994 bytes
downloading Base-1.8.tgz ...
Starting to download Base-1.8.tgz (236,357 bytes)
...done: 236,357 bytes
install ok: channel://components.ez.no/Base-1.8
install ok: channel://components.ez.no/ConsoleTools-1.6.1
install ok: channel://pear.phpunit.de/PHPUnit_SkeletonGenerator-1.2.1