Merge pull request #677 from jeromekelleher/fix-docs

Fix docs build

Author: jeromekelleher

docs/installation.rst

@@ -4,7 +4,7 @@
 Installation
 ############
 
-Python 3.6 or newer is required for ``tsinfer``. Any Unix-like platform should
+Python 3.7 or newer is required for ``tsinfer``. Any Unix-like platform should
 work (``tsinfer`` is tested on Linux, OS X, and Windows).
 
 ***************
@@ -67,4 +67,4 @@ Potential issues
    (see https://github.com/tskit-dev/tsinfer/issues/376). The current workaround is
    either to compile from source by installing alternative python and C compilers via
    conda (``conda install -c conda-forge c-compiler``) or to install the binary
-   packages via conda as recommended at the top of this page.
+   packages via conda as recommended at the top of this page.

requirements/readthedocs.txt

@@ -1,5 +1,8 @@
+# Pinned 2022-06-15 to get CircleCI build going, but with 
+# no particular rationale for versions since docs build
+# will move to GitHub actions soon. (#678)
 attrs
-six
-setuptools_scm 
-sphinx-argparse
-sphinx_rtd_theme
+setuptools_scm==6.0.1
+sphinx==4.5.0
+sphinx-argparse==0.3.1
+sphinx_rtd_theme==1.0.0