Don't "import site" in sympy's installer

Imported from <a href="http://trac.sagemath.org/sage_trac/ticket/12563">trac #12563</a>.

Diff for the sympy spkg, for review only

Reported by: jdemeyer

Component: packages

CC: 

Report Upstream: N/A

Authors: Jeroen Demeyer

Dependencies: 

Work issues: 

Reviewers: William Stein

Merged in: sage-5.0.beta6

Attachments: <ol><li><a href="http://trac.sagemath.org/sage_trac/attachment/ticket/12563/sympy-0.7.1.p0.diff">sympy-0.7.1.p0.diff: Diff for the sympy spkg, for review only</a> by jdemeyer at 20120223T17:38:06</li></ol>