Add words about 3.8

Author: nedbat

CHANGES.rst

@@ -41,6 +41,12 @@ Unreleased
 
 .. _issue 170: https://github.com/nedbat/coveragepy/issues/170
 
+- Tentative support for Python 3.8, which has not yet released an alpha. Fixes
+  `issue 707` and `issue 714`_.
+
+.. _issue 707: https://github.com/nedbat/coveragepy/issues/707
+.. _issue 714: https://github.com/nedbat/coveragepy/issues/714
+
 - Environment variable substitution in configuration files now supports two
   syntaxes for controlling the behavior of undefined variables: if ``VARNAME``
   is not defined, ``${VARNAME?}`` will raise an error, and ``${VARNAME-default

README.rst

@@ -35,7 +35,7 @@ library to determine which lines are executable, and which have been executed.
 Coverage.py runs on many versions of Python:
 
 * CPython 2.7.
-* CPython 3.4 through 3.7.
+* CPython 3.4 through 3.8.
 * PyPy2 6.0 and PyPy3 6.0.
 * Jython 2.7.1, though not for reporting.
 * IronPython 2.7.7, though not for reporting.

doc/index.rst

@@ -80,7 +80,7 @@ not.
     The latest version is coverage.py 5.0a2, released September 3rd 2018.
     It is supported on:
 
-    * Python versions 2.7, 3.4, 3.5, 3.6, and 3.7.
+    * Python versions 2.7, 3.4, 3.5, 3.6, 3.7, and pre-alpha 3.8.
 
     * PyPy2 6.0 and PyPy3 6.0.