Remove unused imports and fix some other linter errors.

recipe_engine/package.py

 # Copyright 2015 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
-import ast
-import collections
-import contextlib
 import copy
 import difflib
-import functools
-import itertools
 import logging
 import operator
 import os
 import subprocess
 import sys
-import tempfile
 
 from . import env
 
 from google.protobuf import text_format
 from . import package_pb2
 from . import fetch
 
 
 class InconsistentDependencyGraphError(Exception):
   def __init__(self, project_id, specs):
@@ skipping 194 matching lines @@
     return buf
 
   def updates(self, context, other_revision=None):
     """Returns a list of all updates to the branch since the revision this
     repo spec refers to.
     """
     raw_updates = self.raw_updates(
         context, (other_revision or self.backend.branch_spec(self.branch)))
     updates = []
     for rev in raw_updates:
+      # TODO(somebody): 'info' is not used.
       info = self._get_commit_info(rev, context)

[Vadim Sh., 2017/02/21 05:46:26]

Looks like unnecessary call, unless self.backend actually keeps some state
internally, updated by _get_commit_info...

       updates.append(GitRepoSpec(
           self.project_id,
           self.repo,
           self.branch,
           rev,
           self.path,
           self.backend))
     return updates
 
   def commit_infos(self, context, other_revision):
@@ skipping 123 matching lines @@
 
   This is accessed by loader.py through RecipeDeps.get_package.
   """
   def __init__(self, name, repo_spec, deps, repo_root, relative_recipes_dir):
     self.name = name
     self.repo_spec = repo_spec
     self.deps = deps
     self.repo_root = repo_root
     self.relative_recipes_dir = relative_recipes_dir
 
-  def __repr__(self):

[Vadim Sh., 2017/02/21 05:46:26]

was defined twice (second definition on line 404, kept it)

-    return '<Package(name=%r,repo_spec=%r,deps=%r,recipes_dir=%r)>' % (
-        self.name, self.repo_spec, self.deps, self.recipes_dir)
-
   @property
   def recipes_dir(self):
     return os.path.join(self.repo_root, self.relative_recipes_dir)
 
   @property
   def recipe_dir(self):
     return os.path.join(self.recipes_dir, 'recipes')
 
   @property
   def module_dir(self):
@@ skipping 302 matching lines @@
   >>> d = { 'x': 1, 'y': 2 }
   >>> sorted(_updated(d, { 'y': 3, 'z': 4 }).items())
   [('x', 1), ('y', 3), ('z', 4)]
   >>> sorted(d.items())
   [('x', 1), ('y', 2)]
   """
 
   d = copy.copy(d)
   d.update(updates)
   return d