function logProgramError(gl, program, vertexShader, fragmentShader) {
    // if linking fails, then log and cleanup
    if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
        if (!gl.getShaderParameter(vertexShader, gl.COMPILE_STATUS)) {
            logPrettyShaderError(gl, vertexShader);
        }
        if (!gl.getShaderParameter(fragmentShader, gl.COMPILE_STATUS)) {
            logPrettyShaderError(gl, fragmentShader);
        }
        console.error('PixiJS Error: Could not initialize shader.');
        // if there is a program info log, log it
        if (gl.getProgramInfoLog(program) !== '') {
            console.warn('PixiJS Warning: gl.getProgramInfoLog()', gl.getProgramInfoLog(program));
        }
    }
}
logs out any program errors
@param gl - The current WebGL context
@param program - the WebGL program to display errors for
@param vertexShader  - the fragment WebGL shader program
@param fragmentShader - the vertex WebGL shader program