Index: pym/portage/dbapi/vartree.py
===================================================================
--- pym/portage/dbapi/vartree.py	(revision 14747)
+++ pym/portage/dbapi/vartree.py	(working copy)
@@ -1819,13 +1819,14 @@
 		This is called before an after any modifications, so that consumers
 		can use directory mtimes to validate caches. See bug #290428.
 		"""
-		base = self.root + _os.sep + VDB_PATH
+		base = os.path.join(self.root, VDB_PATH)
 		cat = catsplit(cpv)[0]
-		catdir = base + _os.sep + cat
+		catdir = os.path.join(base, cat)
 		t = time.time()
 		t = (t, t)
 		for x in (catdir, base):
-			os.utime(x, t)
+			if os.path.lexists(x):
+				os.utime(x, t)
 
 	def cpv_exists(self, mykey):
 		"Tells us whether an actual ebuild exists on disk (no masking)"