It could be that lib.so.6 isn't located where Python is looking for it.
Do:
locate libc.so.6
Then you could try to do a link from the file to the location where Python is looking (/lib/x86_64-linux-gnu/libc.so.6
according to your post).
UPDATE:
You need to update your version of glibc. Look at this post which discussed how to it for Debian: How to upgrade glibc from version 2.13 to 2.15 on Debian?