Travis builds fail with "WARNING: duplicate citation"

[soupault]

Have seen this many times for recent PRs. Consistently fails on [u'seam_carve and [R383]. Restarting build (1 time) fixes the hiccup.

Travis log cut:

...
reading sources... [100%] user_guide/viewer                                     
Warning, treated as error:
[u'seam_carve(img, energy_map, mode, num, border=1, force_copy=True)', u':module: 
skimage.transform', u'', u'', u'', u'Carve vertical or horizontal seams off an image.', u'', u'Carves out 
vertical/horizontal seams from an image while using the given', u'energy map to decide the 
importance of each pixel.', u'', u':Parameters:', u'', u'    **image** : (M, N) or (M, N, 3) ndarray', u'', u'        
Input image whose seams are to be removed.', u'', u'    **energy_map** : (M, N) ndarray', u'', u'        
The array to decide the importance of each pixel. The higher', u'        the value corresponding to a 
pixel, the more the algorithm will try', u'        to keep it in the image.', u'', u"    **mode** : str 
{'horizontal', 'vertical'}", u'', u'        Indicates whether seams are to be removed vertically or 
horizontally.', u'        Removing seams horizontally will decrease the height whereas removing', u'        
vertically will decrease the width.', u'', u'    **num** : int', u'', u'        Number of seams are to be 
removed.', u'', u'    **border** : int, optional', u'', u'        The number of pixels in the right, left and 
bottom end of the image', u'        to be excluded from being considered for a seam. This is important 
as', u'        certain filters just ignore image boundaries and set them to `0`.', u'        By default border 
is set to `1`.', u'', u'    **force_copy** : bool, optional', u'', u'        If set, the `image` and `energy_map` 
are copied before being used by', u'        the method which modifies it in place. Set this to `False` if 
the', u'        original image and the energy map are no longer needed after', u'        this opetration.', 
u'', u':Returns:', u'', u'    **out** : ndarray', u'', u'        The cropped image with the seams removed.', 
u'', u'.. rubric:: References', u'', u'.. [R383] Shai Avidan and Ariel Shamir', u'       "Seam Carving for 
Content-Aware Image Resizing"', u'       
http://www.cs.jhu.edu/~misha/ReadingSeminar/Papers/Avidan07.pdf', u'', u'.. only:: latex', u'', u'   
[R383]_']:52: WARNING: duplicate citation R383, other instance in /home/travis/build/scikit-
image/scikit-image/doc/source/api/skimage.util.txt
make[1]: *** [html] Error 1
make[1]: Leaving directory `/home/travis/build/scikit-image/scikit-image/doc'
make: *** [html] Error 2
The command "tools/travis_script.sh" exited with 2.

[blink1073]

We could allow the docs to retry, much quicker than restarting the whole build ;)

[soupault]

See https://travis-ci.org/scikit-image/scikit-image/jobs/134772208 for the last fail so far.

[jni]

Does anyone have any idea about what's causing this? Race condition?

[sciunto]

I'm closing this one as there is now a "Meta issue"