title: Error while loading skimage camera images
body: <p>I was trying <a href="https://scikit-image.org/docs/stable/user_guide/numpy_images.html#numpy" rel="nofollow noreferrer">a crash course on NumPy for images</a> and this line threw an error:</p>
  
  <pre><code>&gt;&gt; from skimage import data
  &gt;&gt; camera = data.camera()
  </code></pre>
  
  <p>Following is the error trace of the same:</p>
  
  <pre><code>---------------------------------------------------------------------------
  AttributeError                            Traceback (most recent call last)
  &lt;ipython-input-6-8539ecc9e129&gt; in &lt;module&gt;
  ----&gt; 1 data.camera()
  
  ~/.local/lib/python3.6/site-packages/skimage/data/__init__.py in camera()
      107         Camera image.
      108     """
  --&gt; 109     return _load("camera.png")
      110 
      111 
  
  ~/.local/lib/python3.6/site-packages/skimage/data/__init__.py in _load(f, as_gray)
       94     # we lazy import it here
       95     from ..io import imread
  ---&gt; 96     return imread(_os.path.join(data_dir, f), plugin='pil', as_gray=as_gray)
       97 
       98 
  
  ~/.local/lib/python3.6/site-packages/skimage/io/_io.py in imread(fname, as_gray, plugin, **plugin_args)
       46 
       47     with file_or_url_context(fname) as fname:
  ---&gt; 48         img = call_plugin('imread', fname, plugin=plugin, **plugin_args)
       49 
       50     if not hasattr(img, 'ndim'):
  
  ~/.local/lib/python3.6/site-packages/skimage/io/manage_plugins.py in call_plugin(kind, *args, **kwargs)
      208                                (plugin, kind))
      209 
  --&gt; 210     return func(*args, **kwargs)
      211 
      212 
  
  ~/.local/lib/python3.6/site-packages/skimage/io/_plugins/pil_plugin.py in imread(fname, dtype, img_num, **kwargs)
       34         with open(fname, 'rb') as f:
       35             im = Image.open(f)
  ---&gt; 36             return pil_to_ndarray(im, dtype=dtype, img_num=img_num)
       37     else:
       38         im = Image.open(fname)
  
  ~/.local/lib/python3.6/site-packages/skimage/io/_plugins/pil_plugin.py in pil_to_ndarray(image, dtype, img_num)
       64     while 1:
       65         try:
  ---&gt; 66             image.seek(i)
       67         except EOFError:
       68             break
  
  ~/.local/lib/python3.6/site-packages/PIL/PngImagePlugin.py in seek(self, frame)
      737 
      738     def seek(self, frame):
  --&gt; 739         if not self._seek_check(frame):
      740             return
      741         if frame &lt; self.__frame:
  
  ~/.local/lib/python3.6/site-packages/PIL/ImageFile.py in _seek_check(self, frame)
      304             raise EOFError("attempt to seek outside sequence")
      305 
  --&gt; 306         return self.tell() != frame
      307 
      308 
  
  ~/.local/lib/python3.6/site-packages/PIL/PngImagePlugin.py in tell(self)
      825 
      826     def tell(self):
  --&gt; 827         return self.__frame
      828 
      829     def load_prepare(self):
  
  AttributeError: 'PngImageFile' object has no attribute '_PngImageFile__frame'
  </code></pre>
  
  <p>What is the problem here? I'm using <strong>skimage 0.16.2</strong>, <strong>Python 3.6.9</strong> on <strong>Ubuntu 18.04.3 LTS</strong>.</p>
  
  <p>I have plenty of experience with Scikit-Learn but a newbie to image processing and skimage.</p>