MNT linting fixes

[kroq-gar78]

Resolves several issues caught by linter:

• Consistent whitespace
• Removes unused imports and sorts current imports (ruff check --select=I --fix)
• Explicit imports instead of from [...] import *
• Removes some Python 2-specific logic

[Copilot]

Pull request overview

This PR applies linting fixes to improve code quality and consistency across the cottoncandy codebase. The changes focus on modernizing the code by removing Python 2 compatibility logic and improving import organization.

Key changes include:

• Added ruff configuration to pyproject.toml for standardized linting
• Replaced wildcard imports with explicit imports for better code clarity
• Removed Python 2-specific compatibility code (e.g., cPickle, raw_input, configparser fallback)
• Standardized whitespace formatting and import sorting

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
pyproject.toml	Added ruff linter configuration with line length and exclusions
cottoncandy/utils.py	Reorganized imports (removed unused, sorted), fixed whitespace, simplified exception handling, removed Python 2 compatibility
cottoncandy/s3client.py	Replaced wildcard import with explicit imports, removed Python 2 compatibility for pickle and urllib
cottoncandy/options.py	Removed Python 2 configparser fallback and sys.version_info checks
cottoncandy/localclient.py	Consolidated imports and removed Python 2 StringIO fallback
cottoncandy/interfaces.py	Reorganized imports, improved formatting, removed unused glob import
cottoncandy/gdriveclient.py	Replaced raw_input with input, removed Python 2 compatibility check
cottoncandy/browser.py	Reduced imports to only used functions, improved formatting
cottoncandy/backend.py	Updated class definitions to Python 3 style, added whitespace
cottoncandy/appdirs.py	Added consistent whitespace between function definitions
cottoncandy/init.py	Removed unused imports

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[Copilot]

The formatting change here introduces a logic error. The original code was likely:

sdir_copy = 'NUM_%s'%sdir_copy if has_start_digit(sdir) else sdir_copy

This means: prepend 'NUM_' only if the string starts with a digit, otherwise use the original string.

The current code evaluates to:

sdir_copy = 'NUM_%s' % (sdir_copy if has_start_digit(sdir) else sdir_copy)

This always formats the string with 'NUM_%s', regardless of whether it starts with a digit, because the conditional only determines which version of sdir_copy to use (which are the same).

Suggested change

	sdir_copy = 'NUM_%s' % (sdir_copy if has_start_digit(sdir) else sdir_copy)
	sdir_copy = 'NUM_%s' % sdir_copy if has_start_digit(sdir) else sdir_copy

[Copilot]

This commented-out import should be removed rather than left in the code. If it's being kept as documentation of what was replaced, consider removing it entirely since the git history shows the change.

Suggested change

#from .utils import *

[Copilot]

Class GzipInputStream is returned as an iterator (by iter) but does not fully implement the iterator interface.