This fixes commit 3817aa59.

Let's pass the data as function parameters. This greatly simplifies when
using monkey-patching to apply fixers on code that is compiled, for
example. Otherwise, we need to also monkey-patch the code that compile
that code (to change the name).

We can then execute the following query, for example, to find out the
bits of code for which there is no information traced at runtime:

(This is an example for the "division" problem)

SELECT filename
FROM modified
WHERE fixer = "division"
AND filename NOT IN
  (SELECT filename
   FROM division)

The except_clause which are in the "try", "else", or "finally" sections
were detected by mistake.

This is a fixup for commit 3aded8e0.

':' is too common; it can be used in the filename.

This is a fixup for commit a73f5fea.

Note: fixers -> fixes, because of how test's `fixer_pkg` works.