change version number scheme for distutils

Author: chaimleib

CHANGELOG.md

@@ -5,7 +5,8 @@
 - Add `__slots__` optimization in Node class, should give performance improvement
 - Fixed:
   - Restore universal wheels
-  - Fix bytes/str type incompatibility in setup.py
+  - Bytes/str type incompatibility in setup.py
+  - New version of distutils rejects version suffixes of `.postNN`, use `aNN` instead
 
 ## Version 3.0.2
 - Fixed:

setup.py

@@ -42,7 +42,7 @@ def version_info(target_version):
         p = subprocess.Popen('git describe --tag'.split(), stdout=subprocess.PIPE)
         git_describe = str(p.communicate()[0]).strip()
         release, build, commitish = git_describe.split('-')
-        version = "{0}.post{1}".format(release, build)
+        version = "{0}a{1}".format(target_version, build)
     else:  # This is a RELEASE version
         version = target_version
     return {