xerr: Move Errorv from exc here

It is completely orthogonal to exception handling.

exc/error.go

@@ -177,18 +177,3 @@ func erraddcallingcontext(topfunc string, e *Error) *Error {
 
     return e
 }
-
-// error merging multiple errors (e.g. after collecting them from several parallel workers)
-type Errorv []error
-
-func (ev Errorv) Error() string {
-    if len(ev) == 1 {
-        return ev[0].Error()
-    }
-
-    msg := fmt.Sprintf("%d errors:\n", len(ev))
-    for _, e := range ev {
-        msg += fmt.Sprintf("\t- %s\n", e)
-    }
-    return msg
-}

xerr/xerr.go

+// Copyright (C) 2015-2016  Nexedi SA and Contributors.
+//                          Kirill Smelkov <kirr@nexedi.com>
+//
+// This program is free software: you can Use, Study, Modify and Redistribute
+// it under the terms of the GNU General Public License version 3, or (at your
+// option) any later version, as published by the Free Software Foundation.
+//
+// This program is distributed WITHOUT ANY WARRANTY; without even the implied
+// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+//
+// See COPYING file for full licensing terms.
+
+// Package xerr provides addons for error-handling
+package xerr
+
+import (
+    "fmt"
+)
+
+// error merging multiple errors (e.g. after collecting them from several parallel workers)
+type Errorv []error
+
+func (ev Errorv) Error() string {
+    if len(ev) == 1 {
+        return ev[0].Error()
+    }
+
+    msg := fmt.Sprintf("%d errors:\n", len(ev))
+    for _, e := range ev {
+        msg += fmt.Sprintf("\t- %s\n", e)
+    }
+    return msg
+}