old_contents: from __future__ import with_statement
  import re
  
  from webassets.test import TempDirHelper, TempEnvironmentHelper
  
  
  __all__ = ('TempDirHelper', 'TempEnvironmentHelper', 'noop',
             'assert_raises_regexp', 'check_warnings')
  
  
  # Define a noop filter; occasionally in tests we need to define
  # a filter to be able to test a certain piece of functionality,.
  noop = lambda _in, out: out.write(_in.read())
  
  
  try:
      # Python 3
      from nose.tools import assert_raises_regex
  except ImportError:
      try:
          # Python >= 2.7
          from nose.tools import assert_raises_regexp as assert_raises_regex
      except:
          # Python < 2.7
          from nose.tools import set_trace; set_trace()
          def assert_raises_regex(expected, regexp, callable, *a, **kw):
              try:
                  callable(*a, **kw)
              except expected as e:
                  if isinstance(regexp, basestring):
                      regexp = re.compile(regexp)
                  if not regexp.search(str(e.message)):
                      raise self.failureException('"%s" does not match "%s"' %
                               (regexp.pattern, str(e.message)))
              else:
                  if hasattr(expected,'__name__'): excName = expected.__name__
                  else: excName = str(expected)
                  raise AssertionError("%s not raised" % excName)
  
  
  try:
      from test.support import check_warnings  # Python 3
  except ImportError:
  
      try:
          from test.test_support import check_warnings   # Python 2
      except ImportError:
          # Python < 2.6
          import contextlib
  
          @contextlib.contextmanager
          def check_warnings(*filters, **kwargs):
              # We cannot reasonably support this, we'd have to copy to much code.
              # (or write our own). Since this is only testing warnings output,
              # we might slide by ignoring it.
              yield
  
new_contents: from __future__ import with_statement
  import re
  
  from webassets.test import TempDirHelper, TempEnvironmentHelper
  
  
  __all__ = ('TempDirHelper', 'TempEnvironmentHelper', 'noop',
             'assert_raises_regexp', 'check_warnings')
  
  
  # Define a noop filter; occasionally in tests we need to define
  # a filter to be able to test a certain piece of functionality,.
  noop = lambda _in, out: out.write(_in.read())
  
  
  try:
      # Python 3
      from nose.tools import assert_raises_regex
  except ImportError:
      try:
          # Python >= 2.7
          from nose.tools import assert_raises_regexp as assert_raises_regex
      except:
          # Python < 2.7
          def assert_raises_regex(expected, regexp, callable, *a, **kw):
              try:
                  callable(*a, **kw)
              except expected as e:
                  if isinstance(regexp, basestring):
                      regexp = re.compile(regexp)
                  if not regexp.search(str(e.message)):
                      raise self.failureException('"%s" does not match "%s"' %
                               (regexp.pattern, str(e.message)))
              else:
                  if hasattr(expected,'__name__'): excName = expected.__name__
                  else: excName = str(expected)
                  raise AssertionError("%s not raised" % excName)
  
  
  try:
      from test.support import check_warnings  # Python 3
  except ImportError:
  
      try:
          from test.test_support import check_warnings   # Python 2
      except ImportError:
          # Python < 2.6
          import contextlib
  
          @contextlib.contextmanager
          def check_warnings(*filters, **kwargs):
              # We cannot reasonably support this, we'd have to copy to much code.
              # (or write our own). Since this is only testing warnings output,
              # we might slide by ignoring it.
              yield
  
subject: Remove set_trace() instruction.