Speedup modify module

[sivel]

SUMMARY

This PR implements a few performance enhancements to our ast.NodeVisitor to speed up traversing the AST.

1. Implement a function lookup table, instead of using getattr
2. Override generic_visit to not call visit, eliminating function calls
3. Override generic_visit to not walk expr objects, as imports can only happen within stmt

ISSUE TYPE

• Bugfix Pull Request

COMPONENT NAME

lib/ansible/executor/module_common.py

ADDITIONAL INFORMATION

cProfile of recursive_finder before this change:

     26/1    0.006    0.000    0.247    0.247 executor/module_common.py:696(recursive_finder)

After:

     26/1    0.005    0.000    0.162    0.162 executor/module_common.py:719(recursive_finder)

[nitzmahone]

Taking your/CI's word for it that it still properly descends into imports in try/except, etc. ;) Nice little savings!