old_contents: # Copyright 2017 Google Inc. All rights reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  """Python-only helpers for vim-coverage."""
  
  import os, os.path
  import coverage
  
  
  def GetCoveragePyLines(path, source_file):
    """Get (covered, uncovered) lines for source_file from .coverage file at path.
    """
    prev_cwd = os.getcwd()
    source_file = os.path.abspath(source_file)
    try:
      os.chdir(os.path.isfile(path) and os.path.dirname(path) or path)
      try:
        # Coverage.py 4.0 and higher.
        cov = coverage.Coverage()
      except AttributeError:
        cov = coverage.coverage()
      cov.load()
    finally:
      os.chdir(prev_cwd)
    try:
      # Coverage.py 4.0 and higher.
      covered_lines = cov.data.lines(source_file)
    except TypeError:
      covered_lines = cov.data.line_data()[source_file]
    uncovered_lines = cov.analysis(source_file)[2]
    return (covered_lines, uncovered_lines)
  
new_contents: # Copyright 2017 Google Inc. All rights reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  """Python-only helpers for vim-coverage."""
  
  import os, os.path
  import coverage
  
  
  def GetCoveragePyLines(path, source_file):
    """Get (covered, uncovered) lines for source_file from .coverage file at path.
    """
    prev_cwd = os.getcwd()
    source_file = os.path.abspath(source_file)
    try:
      os.chdir(os.path.isfile(path) and os.path.dirname(path) or path)
      try:
        # Coverage.py 4.0 and higher.
        cov = coverage.Coverage()
      except AttributeError:
        cov = coverage.coverage()
      cov.load()
    finally:
      os.chdir(prev_cwd)
    try:
      # Coverage.py 4.0 and higher.
      covered_lines = cov.data.lines(source_file)
    except TypeError:
      covered_lines = cov.data.line_data()[source_file]
    uncovered_lines = cov.analysis(source_file)[2]
    return (covered_lines or [], uncovered_lines)
  
subject: handle covered_lines being None (#30)