When using init or install option of slapos.recipe.build to
write python code, the traceback were hard to understand, because
the current line was not included in the traceback.
This put the script in linecache before compiling it, so that in
case of error the problematic line appears in traceback.
There is still the "problem" that the traceback line numbers starts
from the beginning of the script and not the actual line from
buildout profile, but this does not seem feasible to adjust the line
numbers, so let's ignore this.