Remove unused imports and fix some other linter errors.

recipe_engine/package.py

Index: recipe_engine/package.py
diff --git a/recipe_engine/package.py b/recipe_engine/package.py
index 957817d079b981a4b85f40ce009c7993b3630041..97c2d2f7968d80ee9b64003753b552037c876a47 100644
--- a/recipe_engine/package.py
+++ b/recipe_engine/package.py
@@ -2,19 +2,13 @@
 # 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
 
@@ -229,6 +223,7 @@ class GitRepoSpec(RepoSpec):
         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,
@@ -373,10 +368,6 @@ class Package(object):
     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)