Clean up Codacy outputs: accept single-character variables

[ajjackson]

A common warning in our Codacy outputs is that one-character variable names don't correspond to the expected "snake-case" conventions. It seems to be using Pylint which prefers variable names of at least three characters. But I really don't see much wrong with the way that we use short variable names; they are always given a narrow scope and conventional meaning, e.g.

• fd for file descriptor in file opening context
• i for integer iterator
• x for function argument in a lambda or list comprehension

A suggested way of tolerating this while still catching some bad short names is to whitelist our favourites, which can be done in the Pylint config: https://stackoverflow.com/questions/21833872/why-does-pylint-object-to-single-character-variable-names

But I don't know where this should live or how it would interact with the Codacy framework.

[rebeccafair]

The Codacy site seems to suggest if we add a Pylint configuration file to the repository root, it will just work. I worry about having too much clutter in Euphonic's root dir but that would be a different issue.