old_contents: """Download files using requests and save them to a target path
  
  Usage example::
  
      import hashlib
      from progressbar import DataTransferBar
      from requests_download import download, HashTracker, ProgressTracker
  
      hasher = HashTracker(hashlib.sha256())
      progress = ProgressTracker(DataTransferBar()
  
      download('https://github.com/takluyver/requests_download/archive/master.zip',
               'requests_download.zip', trackers=(hasher, progress))
  
      assert hasher.hashobj.hexdigest() == '...'
  
  """
  
  import requests
  
  __version__ = '0.1.1'
  
  class TrackerBase(object):
      def on_start(self, response):
          pass
  
      def on_chunk(self, chunk):
          pass
  
      def on_finish(self):
          pass
  
  class ProgressTracker(TrackerBase):
      def __init__(self, progressbar):
          self.progressbar = progressbar
          self.recvd = 0
  
      def on_start(self, response):
          max_value = None
          if 'content-length' in response.headers:
              max_value = int(response.headers['content-length'])
          self.progressbar.start(max_value=max_value)
          self.recvd = 0
  
      def on_chunk(self, chunk):
          self.recvd += len(chunk)
          try:
              self.progressbar.update(self.recvd)
          except ValueError:
              # Probably the HTTP headers lied.
              pass
  
      def on_finish(self):
          self.progressbar.finish()
  
  
  class HashTracker(TrackerBase):
      def __init__(self, hashobj):
          self.hashobj = hashobj
  
      def on_chunk(self, chunk):
          self.hashobj.update(chunk)
  
  def download(url, target, headers=None, trackers=()):
      """Download a file using requests.
  
      This is like urllib.request.urlretrieve, but:
  
      - requests validates SSL certificates by default
      - you can pass tracker objects to e.g. display a progress bar or calculate
        a file hash.
      """
      if headers is None:
          headers = {}
      headers.setdefault('user-agent', 'requests_download/'+__version__)
      r = requests.get(url, headers=headers, stream=True)
      r.raise_for_status()
      for t in trackers:
          t.on_start(r)
  
  
      with open(target, 'wb') as f:
          for chunk in r.iter_content(chunk_size=8192):
              if chunk:
                  f.write(chunk)
                  for t in trackers:
                      t.on_chunk(chunk)
  
      for t in trackers:
          t.on_finish()
  
new_contents: """Download files using requests and save them to a target path
  
  Usage example::
  
      import hashlib
      # progressbar is provided by progressbar2 on PYPI.
      from progressbar import DataTransferBar
      from requests_download import download, HashTracker, ProgressTracker
  
      hasher = HashTracker(hashlib.sha256())
      progress = ProgressTracker(DataTransferBar())
  
      download('https://github.com/takluyver/requests_download/archive/master.zip',
               'requests_download.zip', trackers=(hasher, progress))
  
      assert hasher.hashobj.hexdigest() == '...'
  
  """
  
  import requests
  
  __version__ = '0.1.1'
  
  class TrackerBase(object):
      def on_start(self, response):
          pass
  
      def on_chunk(self, chunk):
          pass
  
      def on_finish(self):
          pass
  
  class ProgressTracker(TrackerBase):
      def __init__(self, progressbar):
          self.progressbar = progressbar
          self.recvd = 0
  
      def on_start(self, response):
          max_value = None
          if 'content-length' in response.headers:
              max_value = int(response.headers['content-length'])
          self.progressbar.start(max_value=max_value)
          self.recvd = 0
  
      def on_chunk(self, chunk):
          self.recvd += len(chunk)
          try:
              self.progressbar.update(self.recvd)
          except ValueError:
              # Probably the HTTP headers lied.
              pass
  
      def on_finish(self):
          self.progressbar.finish()
  
  
  class HashTracker(TrackerBase):
      def __init__(self, hashobj):
          self.hashobj = hashobj
  
      def on_chunk(self, chunk):
          self.hashobj.update(chunk)
  
  def download(url, target, headers=None, trackers=()):
      """Download a file using requests.
  
      This is like urllib.request.urlretrieve, but:
  
      - requests validates SSL certificates by default
      - you can pass tracker objects to e.g. display a progress bar or calculate
        a file hash.
      """
      if headers is None:
          headers = {}
      headers.setdefault('user-agent', 'requests_download/'+__version__)
      r = requests.get(url, headers=headers, stream=True)
      r.raise_for_status()
      for t in trackers:
          t.on_start(r)
  
  
      with open(target, 'wb') as f:
          for chunk in r.iter_content(chunk_size=8192):
              if chunk:
                  f.write(chunk)
                  for t in trackers:
                      t.on_chunk(chunk)
  
      for t in trackers:
          t.on_finish()
  
subject: Fix unbalance parenthesis and info