all: use errgo instead of fmt.Errorf

provider/common/state.go

 // Copyright 2012, 2013 Canonical Ltd.
 // Licensed under the AGPLv3, see LICENCE file for details.
 
 package common
 
 import (
-        "errors"
         "fmt"
 
+        "github.com/juju/errgo/errors"
+
         "launchpad.net/juju-core/environs"
         "launchpad.net/juju-core/environs/bootstrap"
         "launchpad.net/juju-core/environs/config"
         "launchpad.net/juju-core/instance"
         "launchpad.net/juju-core/log"
         "launchpad.net/juju-core/state"
         "launchpad.net/juju-core/state/api"
 )
 
 // getDNSNames queries and returns the DNS names for the given instances,
@@ skipping 41 matching lines @@
 
 // StateInfo is a reusable implementation of Environ.StateInfo, available to
 // providers that also use the other functionality from this file.
 func StateInfo(env environs.Environ) (*state.Info, *api.Info, error) {
         st, err := bootstrap.LoadState(env.Storage())
         if err != nil {
                 return nil, nil, err
         }
         config := env.Config()
         if _, hasCert := config.CACert(); !hasCert {
-                return nil, nil, fmt.Errorf("no CA certificate in environment configuration")
+                return nil, nil, errors.Newf("no CA certificate in environment configuration")
         }
         // Wait for the DNS names of any of the instances
         // to become available.
         log.Debugf("waiting for DNS name(s) of state server instances %v", st.StateInstances)
         var hostnames []string
         for a := LongAttempt.Start(); len(hostnames) == 0 && a.Next(); {
                 insts, err := env.Instances(st.StateInstances)
                 if err != nil && err != environs.ErrPartialInstances {
                         log.Debugf("error getting state instances: %v", err.Error())
                         return nil, nil, err
                 }
                 hostnames = getDNSNames(insts)
         }
 
         if len(hostnames) == 0 {
-                return nil, nil, fmt.Errorf("timed out waiting for mgo address from %v", st.StateInstances)
+                return nil, nil, errors.Newf("timed out waiting for mgo address from %v", st.StateInstances)
         }
 
         stateInfo, apiInfo := getStateInfo(config, hostnames)
         return stateInfo, apiInfo, nil
 }