[errors] Greatly simplify common/errors package.

cipd/client/cipd/ensure/package_def.go

Index: cipd/client/cipd/ensure/package_def.go
diff --git a/cipd/client/cipd/ensure/package_def.go b/cipd/client/cipd/ensure/package_def.go
index 1efe662c820ed186b44f3b4c33c69f1a4160a7d3..798e01d0b0689b319443488c4ae61c6aa6ca90dd 100644
--- a/cipd/client/cipd/ensure/package_def.go
+++ b/cipd/client/cipd/ensure/package_def.go
@@ -47,19 +47,13 @@ func (p *PackageDef) Resolve(rslv VersionResolver, templateArgs map[string]strin
 		return
 	}
 	if err != nil {
-		err = errors.Annotate(err).
-			Reason("failed to resolve package template (line %(line)d)").
-			D("line", p.LineNo).
-			Err()
+		err = errors.Annotate(err, "failed to resolve package template (line %d)", p.LineNo).Err()
 		return
 	}
 
 	pin, err = rslv(pin.PackageName, p.UnresolvedVersion)
 	if err != nil {
-		err = errors.Annotate(err).
-			Reason("failed to resolve package version (line %(line)d)").
-			D("line", p.LineNo).
-			Err()
+		err = errors.Annotate(err, "failed to resolve package version (line %d)", p.LineNo).Err()
 		return
 	}