pin Pillow because of build failure

basnijholt · basnijholt · commit 49aac1b6c038 · 2021-03-07T15:22:58.000+01:00
diff --git a/docs/environment.yml b/docs/environment.yml
@@ -18,5 +18,6 @@ dependencies:
   - sphinx_fontawesome=0.0.6
   - sphinx=3.2.1
   - m2r2=0.2.7
+  - pillow=8.0.0 # pin because bokeh incompatibility
   - pip:
     - sphinx_rtd_theme
