Update sling_extract_asf.py

Changes for md5sum due to issues with ASF API

frameMetadata/sling_extract_asf.py

@@ -198,7 +198,16 @@ def get_slc_checksum_md5_asf(slc_id):
         # {u'type': u'FeatureCollection', u'features': []} if SLC not found in ASF
         raise RuntimeError("SLC_ID {} not found in ASF: no available md5 checksum for SLC".format(slc_id))
 
-    md5_hash = geojson["features"][0]["properties"]["md5sum"]  # md5 checksum is lower case
+    md5_hash = ''
+    for thisDict in geojson["features"]:
+        if thisDict["properties"]["processingLevel"] == "SLC":
+            md5_hash = thisDict["properties"]["md5sum"]
+            break
+
+    if not md5_hash:
+        raise RuntimeError("Unable to retreive md5sum hash from query: {}, \n {}".format(asf_geo_json_endpoint,req.text))
+
+#     md5_hash = geojson["features"][0]["properties"]["md5sum"]  # md5 checksum is lower case
     return md5_hash