Ignore unreleased Python versions

Because Python 3.8 prereleases are already out and some people have
already added them to their tox.ini etc., but you cannot enable 3.8 on
Travis or Appveyor yet.

So let's treat 3.8 like we treat -dev releases.

Fixes #1 (the other half).

CHANGES.rst

@@ -1,10 +1,10 @@
 Changelog
 =========
 
-0.11.1 (unreleased)
+0.12.0 (unreleased)
 -------------------
 
-- Nothing changed yet.
+- Ignore unreleased Python versions (3.8 at the moment).
 
 
 0.11.0 (2019-02-13)

check_python_versions.py

@@ -34,7 +34,7 @@
 
 
 __author__ = 'Marius Gedminas <marius@gedmin.as>'
-__version__ = '0.11.1.dev0'
+__version__ = '0.12.0.dev0'
 
 
 log = logging.getLogger('check-python-versions')
@@ -409,10 +409,11 @@ def get_manylinux_python_versions(filename=MANYLINUX_INSTALL_SH):
 
 
 def important(versions):
+    upcoming_release = f'3.{CURRENT_PYTHON_3_VERSION + 1}'
     return {
         v for v in versions
         if not v.startswith(('PyPy', 'Jython')) and v != 'nightly'
-        and not v.endswith('-dev')
+        and not v.endswith('-dev') and v != upcoming_release
     }
 
 

tests.py

@@ -468,9 +468,10 @@ def test_get_manylinux_python_versions(tmp_path):
     ]
 
 
-def test_important():
+def test_important(monkeypatch):
+    monkeypatch.setattr(cpv, 'CURRENT_PYTHON_3_VERSION', 7)
     assert cpv.important({
-        '2.7', '3.4', '3.7-dev', 'nightly', 'PyPy3', 'Jython'
+        '2.7', '3.4', '3.7-dev', '3.8', 'nightly', 'PyPy3', 'Jython'
     }) == {'2.7', '3.4'}