add some error handling for image fetcher

.gitignore

@@ -0,0 +1 @@
+specimen_img_raw/*.jpg

image_fetch.py

@@ -1,5 +1,6 @@
 import glob
 import time
+import urllib.error
 import urllib.request
 
 import requests
@@ -30,7 +31,14 @@ with open("barcode_cleaned.csv") as bcfile:
 
         rdf_url = "https://www.botanicalcollections.be/specimen/" + barcode + "/rdf"
         print("fetching", rdf_url)
+        try:
             img_url = find_image(rdf_url)
+        except urllib.error.HTTPError as er:
+            print("Error on ", rdf_url, str(er))
+            continue
+        if img_url is None:
+            print("Error. No image for barcode.")
+            continue
         img_ext = str(img_url).rsplit(".", 1)[1]
         print("image url:", img_url)
         save_path = "specimen_img_raw/" + barcode + "." + img_ext