Add rule to ignore .pyc files
"Use 4 spaces per indentation level."

from PEP 8 - Style Guide for Python Code
http://www.python.org/dev/peps/pep-0008/#indentation
Use "lowercase with words separated by underscores" for variable names

From PEP 8 - Style Guide for Python Code
http://www.python.org/dev/peps/pep-0008/#method-names-and-instance-variables
Remove empty line at end of file
"Avoid extraneous whitespace (...) immediately inside parentheses (...)"

Also inside brackets and braces.

From PEP 8 - Style Guide for Python Code
http://www.python.org/dev/peps/pep-0008/#pet-peeves
Break long lines after binary operator %, not before

From PEP 8 - Style Guide for Python Code
http://www.python.org/dev/peps/pep-0008/#maximum-line-length
Use implied line continuation inside parentheses...

... instead of backslash at end of line

From PEP 8 - Style Guide for Python Code
http://www.python.org/dev/peps/pep-0008/#maximum-line-length
Prepare Exercise 4

I added the initial code and assertions for examples
adapted from examples run in the interpreter in the book.

I also added assertions for examples presented in the table
listing all different interval names.
Add assertions for intervals close to new examples to be supported

In order to check the interval names to expect for the doubly augmented
and doubly diminished intervals given as example, I first added
assertions for the closest simply augmented and simply diminished
intervals supported by current implementation.
Add assertions for examples of doubly augmented/diminished intervals
Complete exercise 4

I added the new values in the quality map, and adapted the index map
by decrementing all values to shift the neutral position in the quality
map by 1 and offset the value introduced at the start of the quality map.