I fixed a build problem for OpenColorIO for EPEL 7 a few weeks ago and was able to do mockbuilds. I just forced a Koschei rebuild to clear the failure but the build failed[1] for an unusual reason:

In file included from /builddir/build/BUILD/OpenColorIO-1.0.9/src/apps/ociodisplay/main.cpp:46:0:
/usr/include/GL/glext.h:12066:105: error: conflicting declaration 'typedef void (* PFNGLFRAGMENTLIGHTFVSGIXPROC)(GLenum, GLenum, const GLfloat*)'
 typedef void (APIENTRYP PFNGLFRAGMENTLIGHTFVSGIXPROC) (GLenum light, GLenum pname, const GLfloat *params);
                                                                                                         ^
In file included from /builddir/build/BUILD/OpenColorIO-1.0.9/src/apps/ociodisplay/main.cpp:44:0:
/usr/include/GL/glew.h:14376:28: error: 'PFNGLFRAGMENTLIGHTFVSGIXPROC' has a previous declaration as 'typedef void (* PFNGLFRAGMENTLIGHTFVSGIXPROC)(GLenum, GLenum, GLfloat*)'
 typedef void (GLAPIENTRY * PFNGLFRAGMENTLIGHTFVSGIXPROC) (GLenum light, GLenum pname, GLfloat* params);