Why is CPython 2.5 a dependency for Jython 2.5?

[rusi]

On Wednesday, July 3, 2013 5:52:12 PM UTC+5:30, Steven D'Aprano wrote:
> I'm running a box with Debian squeeze, and I just ran:
> sudo aptitude install jython
> which ended up installing Python 2.5:

BTW trying to install jython out here gave me this list
(which does not seem to have this dependency):

$ sudo aptitude install jython
The following NEW packages will be installed:
antlr3{a} ca-certificates-java{a} default-jdk{a} default-jre{a} 
  default-jre-headless{a} icedtea-6-jre-cacao{a} icedtea-6-jre-jamvm{a} 
  icedtea-netx{a} icedtea-netx-common{a} jython libantlr-java{a} 
  libasm4-java{a} libatk-wrapper-java{a} libatk-wrapper-java-jni{a} 
  libconstantine-java{a} libguava-java{a} libjaffl-java{a} libjffi-java{a} 
  libjffi-jni{a} libjnr-netdb-java{a} libjnr-posix-java{a} 
  libjnr-x86asm-java{a} libjsr305-java{a} liblivetribe-jsr223-java{a} 
  libreadline-java{a} libstringtemplate-java{a} openjdk-6-jdk{a} 
  openjdk-6-jre{a} openjdk-6-jre-headless{a} openjdk-6-jre-lib{a} 
  tzdata-java{a} 

$ cat /etc/debian_version
jessie/sid

[And python2.5 is not installed]