Merge pull request #561 from maps-as-data/rwood-97-patch-1

Bug fix - update piffle import

Author: rwood-97

mapreader/__init__.py

@@ -1,6 +1,10 @@
 # download
 from mapreader.download.sheet_downloader import SheetDownloader
-from mapreader.download.iiif_downloader import IIIFDownloader
+try:
+    from mapreader.download.iiif_downloader import IIIFDownloader
+except ImportError:
+    print("[WARNING] Piffle not installed, please install it from the `iiif_dataclasses` branch of https://github.com/rwood-97/piffle/tree/iiif_dataclasses")
+    pass
 from mapreader.download.downloader import Downloader
 from mapreader.download.downloader_utils import create_polygon_from_latlons, create_line_from_latlons
 
@@ -53,4 +57,4 @@
 
 def print_version():
     """Print the current version of mapreader."""
-    print(mapreader.__version__)
+    print(mapreader.__version__)