docs: add deprecation warning

5 jobs for master in 59 minutes and 19 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Test
passed test-macos #630883
macos_highsierra

00:17:32

 
  Build
failed build-latest #630884

00:05:09

passed build-nightly #630885

00:41:45

 
  Docs
skipped docs #630886
 
  Deploy
skipped pages #630887
 
Name Stage Failure
failed
build-latest Build
Elapsed: -

An HTTP error occurred when trying to retrieve this URL.
HTTP errors are often intermittent, and a simple retry will get you on your way.
'https://conda.anaconda.org/conda-forge/noarch'


The command '/bin/sh -c conda env create -f /tmp/environment-py27.yml' returned a non-zero code: 1
ERROR: Job failed: exit code 1