Resolve pylint warning: Unused variable 'i'. The _ character is a valid variable in Python, with a special property that pylint and others recognise that it is intended to be unused.
Fix pylint warning: local variable 'outq' is assigned but never read; and unused variable 'outq'
Fix pylint warning: Bare exception not recommended
Fix pylint warning: Refining built-in 'file'
Fix pylint warning: Unused import sys
Fix pylint warning: Unused import os
Fix pylint warning: 'screed' imported but unused
Fix pylint warning: Using possibly undefined loop variable 'input_filename'
Fix pylint warning: Using possibly undefined loop variable 'index'
Fix pylint warning: Unused import threading
Fix pylint warning: Using possibly undefined loop variable 'filename'
Update ChangeLog
Merge pull request #582 from Echelon9/fix/pylint-warnings

Fix pylint warnings
minor fix to normalize-by-median, cleanup of saturate
fix indent in normalize-by-median
Merge pull request #586 from ged-lab/cleanup/normalize_and_saturate

minor fix to normalize-by-median, cleanup of saturate
Add failing tests for Issue #174 (TDD)
Improve quality of error message
Adopt ValueError as the desired Python exception and make more consistent with other negative tests
make diff_pylint_report tweaks