From c2c7b8f3708a3770d2b0416d8112a097d8ab1a45 Mon Sep 17 00:00:00 2001
From: Thomas Robitaille <thomas.robitaille@gmail.com>
Date: Thu, 14 Sep 2017 17:21:06 -0400
Subject: [PATCH] Give a nice error if no data is present in the selected HDU

---
 CHANGES.rst              | 4 ++++
 spectral_cube/io/fits.py | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/CHANGES.rst b/CHANGES.rst
index 3ee1d6ffa..632fc614e 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,5 +1,9 @@
 0.4.1 (unreleased)
 ------------------
+
+ - Raise a nicer error if no data is present in the default or
+   selected HDU
+   (https://github.com/radio-astro-tools/spectral-cube/pull/424)
  - Check mask inputs to OneDSpectrum and add mask handling for
    OneDSpectrum.spectral_interpolate
    (https://github.com/radio-astro-tools/spectral-cube/pull/400)
diff --git a/spectral_cube/io/fits.py b/spectral_cube/io/fits.py
index 062d94b4a..2e4961e5e 100644
--- a/spectral_cube/io/fits.py
+++ b/spectral_cube/io/fits.py
@@ -134,6 +134,10 @@ def load_fits_cube(input, hdu=0, meta=None, **kwargs):
 
     data, header, beam_table = read_data_fits(input, hdu=hdu, **kwargs)
 
+    if data is None:
+        raise Exception('No data found in HDU {0}. You can try using the hdu= '
+                        'keyword argument to read data from another HDU.'.format(hdu))
+
     if meta is None:
         meta = {}