Allow translator based header fix up to go wrong

It's possible that some headers are so broken that the
code trying to fix them up can't work out something.
A date is a good example since an error parsing a date
in a header will cause many date-based corrections to
fail.

Log the problem and hope that a file-based correction
is put in place that allows the translator code to
function properly.

python/astro_metadata_translator/headers.py

@@ -353,6 +353,12 @@ class or else support automatic translation class determination.
         modified = _find_from_resource(header, *translator.resource_root(), target_file)
 
     # Allow a translation class to do local fixups
-    translator_modified = translator_class.fix_header(header)
+    # Allow it to fail but log the failure
+    try:
+        translator_modified = translator_class.fix_header(header)
+    except Exception as e:
+        log.fatal("Ignoring translator header fixup of %s %s: %s",
+                  instrument, obsid, str(e))
+        translator_modified = False
 
     return modified | translator_modified