Fix for Astropy Header not behaving dict-like.

python/astro_metadata_translator/tests.py

@@ -19,6 +19,7 @@
 from astropy.time import Time
 import astropy.utils.exceptions
 import warnings
+from astropy.io.fits import Header
 
 from astro_metadata_translator import ObservationInfo
 
@@ -149,8 +150,26 @@ def assertObservationInfoFromYaml(self, file, dir=None, check_wcs=True,  # noqa:
             inconsistent.
         """
         header = read_test_file(file, dir=dir)
-        self.assertObservationInfo(header, filename=file, check_wcs=check_wcs,
-                                   wcs_params=wcs_params, **kwargs)
+
+        try:
+            self.assertObservationInfo(header, filename=file, check_wcs=check_wcs,
+                                       wcs_params=wcs_params, **kwargs)
+        except AssertionError as e:
+            raise AssertionError("ObservationInfo derived from an dict-like "
+                                 "type is inconsistent.") from e
+
+        astropy_header = Header()
+        for key, val in header.items():
+            values = val if isinstance(val, list) else [val]
+            for v in values:
+                astropy_header[key] = v
+
+        try:
+            self.assertObservationInfo(astropy_header, filename=file, check_wcs=check_wcs,
+                                       wcs_params=wcs_params, **kwargs)
+        except AssertionError as e:
+            raise AssertionError("ObservationInfo derived from an Astropy "
+                                 "Header is inconsistent.") from e
 
     def assertObservationInfo(self, header, filename=None, check_wcs=True,  # noqa: N802
                               wcs_params=None, **kwargs):

python/astro_metadata_translator/translator.py

@@ -668,7 +668,7 @@ def is_keyword_defined(header, keyword):
         is_defined : `bool`
             `True` if the header is present and not-`None`. `False` otherwise.
         """
-        if keyword not in header:
+        if keyword is None or keyword not in header:
             return False
 
         if header[keyword] is None: