Standardize imports

Refactor imports to follow pep8 guidelines of standard library, related
third party and local library order for imports.

Change-Id: Ied624c088c110c56f6e471a1441db0f8d6adae3c

git_upstream/lib/note.py

@@ -15,9 +15,10 @@
 # limitations under the License.
 #
 
-from git_upstream.errors import GitUpstreamError
 from git import base, GitCommandError
 
+from git_upstream.errors import GitUpstreamError
+
 
 class NoteAlreadyExistsError(GitUpstreamError):
     """Exception thrown by note related commands"""

git_upstream/lib/pygitcompat.py

@@ -16,7 +16,12 @@
 #
 
 import git
-from git import Commit, Repo
+
+try:
+    from git.objects.commit import Commit
+    from git.repo import Repo
+except ImportError:
+    from git import Commit, Repo
 
 
 class GitUpstreamCompatRepo(Repo):

git_upstream/lib/rebaseeditor.py

@@ -15,13 +15,13 @@
 # limitations under the License.
 #
 
+import codecs
+import subprocess
+import os
+
 from git_upstream.lib.utils import GitMixin
 from git_upstream.log import LogDedentMixin
 
-from subprocess import call
-import os
-import codecs
-
 REBASE_EDITOR_SCRIPT = "rebase-editor"
 
 # ensure name of file will match any naming filters used by editors to
@@ -152,7 +152,8 @@ class RebaseEditor(GitMixin, LogDedentMixin):
         if self._interactive:
             # spawn the editor
             user_editor = self.git_sequence_editor or self.git_editor
-            status = call("%s %s" % (user_editor, todo_file), shell=True)
+            status = subprocess.call("%s %s" % (user_editor, todo_file),
+                                     shell=True)
             if status:
                 return status, None, "Editor returned non-zero exit code"
 
@@ -171,7 +172,7 @@ class RebaseEditor(GitMixin, LogDedentMixin):
                 cmd = ['git', 'rebase', '--interactive']
                 cmd.extend(self.git.transform_kwargs(**kwargs))
                 cmd.extend(args)
-                return call(cmd), None, None
+                return subprocess.call(cmd), None, None
             else:
                 return self.git.rebase(interactive=True, with_exceptions=False,
                                        with_extended_output=True, *args,

git_upstream/lib/searchers.py

@@ -15,17 +15,13 @@
 # limitations under the License.
 #
 
-from git_upstream.lib.utils import GitMixin
-from git_upstream.log import LogDedentMixin
-
-try:
-    from git.objects.commit import Commit
-except ImportError:
-    from git_upstream.lib.pygitcompat import GitUpstreamCompatCommit as Commit
-
 from abc import ABCMeta, abstractmethod
 import re
 
+from git_upstream.lib.utils import GitMixin
+from git_upstream.lib.pygitcompat import Commit
+from git_upstream.log import LogDedentMixin
+
 
 class Searcher(GitMixin):
     """

git_upstream/lib/utils.py

@@ -15,12 +15,12 @@
 # limitations under the License.
 #
 
-from git_upstream.errors import GitUpstreamError
-from git_upstream.lib.pygitcompat import Repo
-
 import os
 import sys
 
+from git_upstream.errors import GitUpstreamError
+from git_upstream.lib.pygitcompat import Repo
+
 try:
     from git.exc import InvalidGitRepositoryError
 except ImportError:

git_upstream/main.py

@@ -20,27 +20,27 @@
 Command-line tool for tracking upstream revisions
 """
 
+import logging
+import sys
+import argparse
+
 import git
 
-import git_upstream.commands as commands
-from git_upstream.errors import GitUpstreamError
-import git_upstream.log as log
+from git_upstream import commands
+from git_upstream import log
+from git_upstream import subcommand
 from git_upstream import __version__
+from git_upstream.errors import GitUpstreamError
 
-import subcommand
-import argparse
-from argparse import ArgumentParser
 try:
     import argcomplete
     argparse_loaded = True
 except ImportError:
     argparse_loaded = False
-import logging
-import sys
 
 
 def get_parser():
-    parser = ArgumentParser(
+    parser = argparse.ArgumentParser(
         description=__doc__.strip(),
         epilog='See "%(prog)s help COMMAND" for help on a specific command.',
         add_help=False)

git_upstream/rebase_editor.py

@@ -28,7 +28,7 @@ Avoid use of stdin for passing such information as many editors have problems
 if exec'ed and stdin is a pipe.
 """
 
-from argparse import ArgumentParser
+import argparse
 import fileinput
 import os
 import sys
@@ -59,7 +59,7 @@ def rebase_replace_insn(path, istream):
 
 
 def main():
-    parser = ArgumentParser(
+    parser = argparse.ArgumentParser(
         description=__doc__.strip(),
     )
     parser.add_argument('-v', '--verbose', action='store_true', default=False,