MSG - errors "no format arguments" for CplError() when building frmts/msg/msgdataset.cpp

[shot2]

Trunk from 2016/04/12, Ubuntu 14.04 amd64, gcc-4.8 c++0x.

In a paranoid "-Werror=format-security" context, building the MSG/Eumetsat driver fails with

error: format not a string literal and no format arguments

at two places, lines 141 and 186 of frmts/msg/msgdataset.cpp:

CPLError( CE_Failure, CPLE_AppDefined, (sErr+"\n").c_str() );

CPLError( CE_Failure, CPLE_AppDefined,
                  sErr.c_str() );

The issue obviously resides in the lack of a formatting argument for ".c_str()"

[Even Rouault]

trunk r33950, branches/2.1 r33951 "MSG: fix build with -Werror=format-security (reported by shot2, #6451)"