Unable to install with opentracing extras

[goodspark]

I was following the OpenTracing setup instructions but got a warning about missing extras:

(blah-YneZd-6L) sam@sam-Q325UAR ~/t/blah> pip list
Package    Version
---------- -------
pip        18.0   
setuptools 40.4.1 
wheel      0.31.1 

(blah-YneZd-6L) sam@sam-Q325UAR ~/t/blah> python --version
Python 2.7.14

(blah-YneZd-6L) sam@sam-Q325UAR ~/t/blah> pip --version
pip 18.0 from /home/sam/.local/share/virtualenvs/blah-YneZd-6L/lib/python2.7/site-packages/pip (python 2.7)


(blah-YneZd-6L) sam@sam-Q325UAR ~/t/blah> pip install 'ddtrace[opentracing] == 0.14.0'
Collecting ddtrace[opentracing]==0.14.0
  ddtrace 0.14.0 does not provide the extra 'opentracing'
Collecting msgpack-python (from ddtrace[opentracing]==0.14.0)
Collecting wrapt (from ddtrace[opentracing]==0.14.0)
Installing collected packages: msgpack-python, wrapt, ddtrace
Successfully installed ddtrace-0.14.0 msgpack-python-0.5.6 wrapt-1.10.11

ddtrace 0.14.0 does not provide the extra 'opentracing'

Happens on Python 3.6 as well.