Add importlib.util.resolve_name().

Lib/importlib/util.py

@@ -3,3 +3,19 @@
 from ._bootstrap import module_for_loader
 from ._bootstrap import set_loader
 from ._bootstrap import set_package
+from ._bootstrap import _resolve_name
+
+
+def resolve_name(name, package):
+    """Resolve a relative module name to an absolute one."""
+    if not name.startswith('.'):
+        return name
+    elif not package:
+        raise ValueError('{!r} is not a relative name '
+                         '(no leading dot)'.format(name))
+    level = 0
+    for character in name:
+        if character != '.':
+            break
+        level += 1
+    return _resolve_name(name[level:], package, level)