Blacklist pillow 7.1.*

There is a regression in the latest Pillow releases

python-pillow/Pillow#4528
The fix has been merged but not released yet

recipe/meta.yaml

@@ -12,7 +12,7 @@ source:
   # sha256: 3b8414ccb9b524d0d507909e9a4d3843af6ca9919152199d380f2b21639abf17
 
 build:
-  number: 0
+  number: 1
   skip: True  # [py==27]
   script:
     - rm -rf skimage/viewer/tests  # we don't depend on Qt
@@ -46,7 +46,7 @@ requirements:
     - scipy >=0.19
     - matplotlib-base >=2.0.0
     - networkx >=2.0
-    - pillow >=4.3.0
+    - pillow >=4.3.0,!=7.1.*
     - pywavelets >=0.4.0
     - imageio >=2.3.0
     # scikit-image depends on dask-array