vpython: Version parser from PEP440.

vpython/python/python_test.go

 // Copyright 2017 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package python
 
 import (
         "fmt"
         "os"
         "os/exec"
@@ skipping 129 matching lines @@
         if err != nil {
                 t.Fatalf("failed to get executable: %s", err)
         }
         versionString := ""
 
         versionSuccesses := []struct {
                 output string
                 vers   Version
         }{
                 {"Python 2.7.1\n", Version{2, 7, 1}},
+                {"Python 2.7.1+local string", Version{2, 7, 1}},
                 {"Python 3", Version{3, 0, 0}},
+                {"Python 3.1.2.3.4", Version{3, 1, 2}},
         }
 
         versionFailures := []struct {
                 output string
                 err    string
         }{
                 {"", "unknown version output"},
                 {"Python2.7.11\n", "unknown version output"},
                 {"Python", "unknown version output"},
-                {"Python 2.7.11 foo bar junk", "invalid number value"},
-                {"Python 3.1.2.3.4", "failed to parse version"},
+                {"Python 2.7.11 foo bar junk", "non-canonical Python version string"},
         }
 
         Convey(`Testing Interpreter.GetVersion`, t, func() {
                 c := context.Background()
 
                 i := Interpreter{
                         Python: self,
 
                         testCommandHook: func(cmd *exec.Cmd) {
                                 var env environ.Env
@@ skipping 15 matching lines @@
                 for _, tc := range versionFailures {
                         Convey(fmt.Sprintf(`Will fail to parse %q (%s)`, tc.output, tc.err), func() {
                                 versionString = tc.output
 
                                 _, err := i.GetVersion(c)
                                 So(err, ShouldErrLike, tc.err)
                         })
                 }
         })
 }