virtualenv不支持python2.5或以前的版本

wget http://www.python.org/ftp/python/2.5.2/Python-2.5.2.tar.bz2
tar jxvf Python-2.5.2.tar.bz2
cd Python-2.5.2
./configure --prefix=/usr/local/python-2.5.2
make
make install
as3:~/Python-2.5.2# /usr/local/python-2.5.2/bin/python -V
Python 2.5.2
as3:~/Python-2.5.2# cd ~
as3:~# wget https://pypi.python.org/packages/source/s/setuptools/setuptools-1.4.1.tar.gz
as3:~# tar zxvf setuptools-1.4.1.tar.gz
as3:~# cd setuptools-1.4.1
as3:~/setuptools-1.4.1# /usr/local/python-2.5.2/bin/python ez_setup.py
as3:~/setuptools-1.4.1# cd /usr/local/python-2.5.2/bin/
as3:/usr/local/python-2.5.2/bin# ls
as3:/usr/local/python-2.5.2/bin# ls
easy_install      pydoc      python2.5-config  virtualenv
easy_install-2.5  python     python-config     virtualenv-2.5
idle              python2.5  smtpd.py
as3:/usr/local/python-2.5.2/bin#
(/usr/local/python-2.5.2/bin/里新出现了easy_install-2.5这个执行文件）
as3:/usr/local/python-2.5.2/bin# ./easy_install-2.5 virtualenv
显示：
...
Installing virtualenv script to /usr/local/python-2.5.2/bin
Installing virtualenv-2.5 script to /usr/local/python-2.5.2/bin
Installed /usr/local/python-2.5.2/lib/python2.5/site-packages/virtualenv-1.10.1-py2.5.egg
Processing dependencies for virtualenv
Finished processing dependencies for virtualenv
as3:/usr/local/python-2.5.2/bin# ls
easy_install      pydoc      python2.5-config  virtualenv
easy_install-2.5  python     python-config     virtualenv-2.5
idle              python2.5  smtpd.py
as3:/usr/local/python-2.5.2/bin#
(/usr/local/python-2.5.2/bin/里新出现了virtualenv-2.5这个执行文件）
as3:/usr/local/python-2.5.2/bin# /usr/local/python-2.5.2/bin/virtualenv environ-for-pylogs
ERROR: None
ERROR: this script requires Python 2.6 or greater
(可见virtualenv不支持python2.5或以前的版本）