Add error convenience extension

lib/core/libimagerror/src/lib.rs

@@ -39,3 +39,5 @@ extern crate error_chain;
 
 pub mod trace;
 pub mod iter;
+pub mod str;
+

lib/core/libimagerror/src/str.rs

@@ -0,0 +1,31 @@
+//
+// imag - the personal information management suite for the commandline
+// Copyright (C) 2015-2018 the imag contributors
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; version
+// 2.1 of the License.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+//
+
+use std::error::Error;
+
+pub trait ErrFromStr<T> {
+    fn err_from_str(self) -> Result<T, String>;
+}
+
+impl<T, E: Error> ErrFromStr<T> for Result<T, E> {
+    fn err_from_str(self) -> Result<T, String> {
+        self.map_err(|e| format!("{}", e.description()))
+    }
+}
+