old_contents: from os import walk, sep, chdir, pardir
  from os.path import split, join, abspath
  from glob import glob
  
  # System path separator (usually slash or backslash)
  sepd = {"sep": sep}
  
  # Files having at least one of these in their path will be excluded
  EXCLUDE = set([
      "%(sep)sthirdparty%(sep)s" % sepd,
      "%(sep)sprinting%(sep)spretty%(sep)s" % sepd,
  ])
  
  def test_no_trailing_whitespace():
      message = "File contains trailing whitespace: %s, line %s."
      base_path = split(__file__)[0]
      base_path += sep + pardir + sep + pardir # go to sympy/
      base_path = abspath(base_path)
      for root, dirs, files in walk(base_path):
          for fname in glob(join(root, "*.py")):
              if filter(lambda ex: ex in fname, EXCLUDE):
                  continue
              file = open(fname, "r")
              try:
                  for idx, line in enumerate(file):
                      if line.endswith(" \n"):
                          assert False, message % (fname, idx+1)
              finally:
                  file.close()
  
  
new_contents: from os import walk, sep, chdir, pardir
  from os.path import split, join, abspath
  from glob import glob
  
  # System path separator (usually slash or backslash)
  sepd = {"sep": sep}
  
  # Files having at least one of these in their path will be excluded
  EXCLUDE = set([
      "%(sep)sthirdparty%(sep)s" % sepd,
  #    "%(sep)sprinting%(sep)spretty%(sep)s" % sepd,
  ])
  
  def test_no_trailing_whitespace():
      message = "File contains trailing whitespace: %s, line %s."
      base_path = split(__file__)[0]
      base_path += sep + pardir + sep + pardir # go to sympy/
      base_path = abspath(base_path)
      for root, dirs, files in walk(base_path):
          for fname in glob(join(root, "*.py")):
              if filter(lambda ex: ex in fname, EXCLUDE):
                  continue
              file = open(fname, "r")
              try:
                  for idx, line in enumerate(file):
                      if line.endswith(" \n"):
                          assert False, message % (fname, idx+1)
              finally:
                  file.close()
  
subject: Test whitespace in pretty printing tests.