old_contents: # Copyright © 2016 Jakub Wilk <jwilk@jwilk.net>
  #
  # Permission is hereby granted, free of charge, to any person obtaining a copy
  # of this software and associated documentation files (the “Software”), to deal
  # in the Software without restriction, including without limitation the rights
  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  # copies of the Software, and to permit persons to whom the Software is
  # furnished to do so, subject to the following conditions:
  #
  # The above copyright notice and this permission notice shall be included in
  # all copies or substantial portions of the Software.
  #
  # THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  # SOFTWARE.
  
  import concurrent.futures
  import functools
  import sys
  
  def isolation(f):
      if 'coverage' in sys.modules:
          # Process isolation would break coverage measurements.
          # Oh well. FIXME.
          return f
      else:
          @functools.wraps(f)
          def wrapper(*args, **kwargs):
              with concurrent.futures.ProcessPoolExecutor() as executor:
                  ftr = executor.submit(f, *args, **kwargs)
                  return ftr.result()
      return wrapper
  
  __all__ = ['isolation']
  
  # vim:ts=4 sts=4 sw=4 et
  
new_contents: # Copyright © 2016 Jakub Wilk <jwilk@jwilk.net>
  #
  # Permission is hereby granted, free of charge, to any person obtaining a copy
  # of this software and associated documentation files (the “Software”), to deal
  # in the Software without restriction, including without limitation the rights
  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  # copies of the Software, and to permit persons to whom the Software is
  # furnished to do so, subject to the following conditions:
  #
  # The above copyright notice and this permission notice shall be included in
  # all copies or substantial portions of the Software.
  #
  # THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  # SOFTWARE.
  
  import concurrent.futures
  import functools
  import sys
  
  def isolation(f):
      if 'coverage' in sys.modules:
          # Process isolation would break coverage measurements.
          # Oh well. FIXME.
          return f
      else:
          @functools.wraps(f)
          def wrapper(*args, **kwargs):
              with concurrent.futures.ProcessPoolExecutor(max_workers=1) as executor:
                  ftr = executor.submit(f, *args, **kwargs)
                  return ftr.result()
      return wrapper
  
  __all__ = ['isolation']
  
  # vim:ts=4 sts=4 sw=4 et
  
subject: set max_workers=1.