update example to not use stderr

Author: simonrw

fitsio/examples/reading_from_memory.rs

@@ -10,6 +10,8 @@ use std::io::Read;
 #[cfg(all(target_pointer_width = "64", target_os = "linux"))]
 fn main() {
     // read the bytes into memory and return a pointer and length to the file
+
+    use fitsio::errors::check_status;
     let (bytes, mut ptr_size) = {
         let filename = "./testdata/full_example.fits";
         let mut f = std::fs::File::open(filename).unwrap();
@@ -39,10 +41,7 @@ fn main() {
         );
     }
 
-    if status != 0 {
-        unsafe { sys::ffrprt(sys::stderr, status) };
-        panic!("bad status");
-    }
+    check_status(status).unwrap();
 
     let mut f = unsafe { FitsFile::from_raw(fptr, FileOpenMode::READONLY) }.unwrap();
     f.pretty_print().expect("pretty printing fits file");