use pip-compile to pin dev requirements

requirements/docs.txt

@@ -0,0 +1,36 @@
+#
+# This file is autogenerated by pip-compile
+# To update, run:
+#
+#    pip-compile requirements/docs.in
+#
+alabaster==0.7.12         # via sphinx
+babel==2.8.0              # via sphinx
+certifi==2020.4.5.1       # via requests
+chardet==3.0.4            # via requests
+docutils==0.16            # via sphinx
+idna==2.9                 # via requests
+imagesize==1.2.0          # via sphinx
+jinja2==2.11.2            # via sphinx
+markupsafe==1.1.1         # via jinja2
+packaging==20.4           # via -r requirements/docs.in, pallets-sphinx-themes, sphinx
+pallets-sphinx-themes==1.2.3  # via -r requirements/docs.in
+pygments==2.6.1           # via sphinx
+pyparsing==2.4.7          # via packaging
+pytz==2020.1              # via babel
+requests==2.23.0          # via sphinx
+six==1.15.0               # via packaging
+snowballstemmer==2.0.0    # via sphinx
+sphinx-issues==1.2.0      # via -r requirements/docs.in
+sphinx==3.0.3             # via -r requirements/docs.in, pallets-sphinx-themes, sphinx-issues, sphinxcontrib-log-cabinet
+sphinxcontrib-applehelp==1.0.2  # via sphinx
+sphinxcontrib-devhelp==1.0.2  # via sphinx
+sphinxcontrib-htmlhelp==1.0.3  # via sphinx
+sphinxcontrib-jsmath==1.0.1  # via sphinx
+sphinxcontrib-log-cabinet==1.0.1  # via -r requirements/docs.in
+sphinxcontrib-qthelp==1.0.3  # via sphinx
+sphinxcontrib-serializinghtml==1.1.4  # via sphinx
+urllib3==1.25.9           # via requests
+
+# The following packages are considered to be unsafe in a requirements file:
+# setuptools