wip: refuctoring on the road to v201812

src/pycalver/version.py

@@ -6,6 +6,7 @@
 """Functions related to version string manipulation."""
 
 import logging
+import pkg_resources
 import typing as typ
 import datetime as dt
 
@@ -29,7 +30,7 @@ def incr(old_version: str, *, release: str = None) -> str:
     Old_version is assumed to be a valid calver string,
     already validated in pycalver.config.parse.
     """
-    old_ver = parse.VersionInfo.parse(old_version)
+    old_ver = parse.parse_version_info(old_version)
 
     new_calver = current_calver()
 
@@ -60,3 +61,12 @@ def incr(old_version: str, *, release: str = None) -> str:
     if new_release:
         new_version += "-" + new_release
     return new_version
+
+
+def pycalver_to_pep440(version: str) -> str:
+    """Derive pep440 compliant version string from PyCalVer version string.
+
+    >>> pycalver_to_pep440("v201811.0007-beta")
+    '201811.7b0'
+    """
+    return str(pkg_resources.parse_version(version))