Providers are responsible for selecting tools

environs/tools/storage.go

 // Copyright 2013 Canonical Ltd.
 // Licensed under the AGPLv3, see LICENCE file for details.
 
 package tools
 
 import (
         "errors"
         "strings"
 
         "launchpad.net/juju-core/environs/storage"
@@ skipping 29 matching lines @@
         }
         var list coretools.List
         var foundAnyTools bool
         for _, name := range names {
                 if !strings.HasPrefix(name, toolPrefix) || !strings.HasSuffix(name, toolSuffix) {
                         continue
                 }
                 var t coretools.Tools
                 vers := name[len(toolPrefix) : len(name)-len(toolSuffix)]
                 if t.Version, err = version.ParseBinary(vers); err != nil {
+                        logger.Debugf("failed to parse version %q: %v", vers, err)
                         continue
                 }
                 foundAnyTools = true
                 // Major version must match specified value.
                 if t.Version.Major != majorVersion {
                         continue
                 }
                 // If specified minor version value supplied, minor version must match.
                 if minorVersion >= 0 && t.Version.Minor != minorVersion {
                         continue
                 }
                 logger.Debugf("found %s", vers)
                 if t.URL, err = stor.URL(name); err != nil {
                         return nil, err
                 }
                 list = append(list, &t)
         }
         if len(list) == 0 {
                 if foundAnyTools {
                         return nil, coretools.ErrNoMatches
                 }
                 return nil, ErrNoTools
         }
         return list, nil
 }