Note an alias works when calling it. If you use it as a parameter of another command, it is not interpreted. Hence, in your mkvirtualenv ...
you should specify explicitly the path of this python.
Otherwise, you can set a variable
mypython276=/opt/python276/bin/python2.7
and then do
mkvirtualenv test -p $mypython276
As said in comments, you can also add /opt/python3.3/bin/
into the PATH
variable.