[errors] Greatly simplify common/errors package.

vpython/application/probe.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 application
 
 import (
         "fmt"
         "os"
         "os/exec"
@@ skipping 86 matching lines @@
 // the LookPathResult.
 func (lp *lookPath) checkWrapper(c context.Context, path string, env environ.Env) (isWrapper bool, err error) {
         env.Set(checkWrapperENV, "1")
 
         cmd := exec.CommandContext(c, path, "--version")
         cmd.Env = env.Sorted()
 
         output, err := cmd.CombinedOutput()
         rc, ok := exitcode.Get(err)
         if !ok {
-                err = errors.Annotate(err).Reason("failed to check if %(path)q is a wrapper").
-                        D("path", path).
-                        Err()
+                err = errors.Annotate(err, "failed to check if %q is a wrapper", path).Err()
                 return
         }
 
         // Retain the last output, so our "look" can reference it to extract the
         // version string.
         lp.lastPath = path
         lp.lastOutput = string(output)
 
         if rc != 0 {
                 // The target exited with a non-zero error code. It is a wrapper if it
                 // printed the sentinel text.
                 isWrapper = strings.TrimSpace(lp.lastOutput) == checkWrapperSentinel
                 if isWrapper {
                         // The target was successfully identified as a wrapper. Clear "err", which
                         // is non-nil b/c of the non-zero exit code, to indicate a successful
                         // wrapper check.
                         err = nil
                         return
                 }
 
                 // The target returned non-zero, but didn't identify as a wrapper. It is
                 // likely something that happens to be named the same thing as the target,
                 // which is an error.
-                err = errors.Annotate(err).Reason("wrapper check returned non-zero").Err()
+                err = errors.Annotate(err, "wrapper check returned non-zero").Err()
         }
 
         return
 }