[vpython] Fix PEP425 naming.

vpython/spec/spec.go

Index: vpython/spec/spec.go
diff --git a/vpython/spec/spec.go b/vpython/spec/spec.go
index 97abe5a416423c0c3168657c87a6ee5f3bb28524..42a9a3a0cc917a464b7d5920b046add28a7da69e 100644
--- a/vpython/spec/spec.go
+++ b/vpython/spec/spec.go
@@ -102,15 +102,15 @@ func (s specPackageSlice) Less(i, j int) bool {
 	}.Use(i, j)
 }
 
-type pep425TagSlice []*vpython.Pep425Tag
+type pep425TagSlice []*vpython.PEP425Tag
 
 func (s pep425TagSlice) Len() int      { return len(s) }
 func (s pep425TagSlice) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
 
 func (s pep425TagSlice) Less(i, j int) bool {
 	return sortby.Chain{
-		func(i, j int) bool { return s[i].Version < s[j].Version },
+		func(i, j int) bool { return s[i].Python < s[j].Python },
 		func(i, j int) bool { return s[i].Abi < s[j].Abi },
-		func(i, j int) bool { return s[i].Arch < s[j].Arch },
+		func(i, j int) bool { return s[i].Platform < s[j].Platform },
 	}.Use(i, j)
 }