Support pulling from zenodo sandbox too

Test uploads should go to the sandbox, rather than to
main zenodo. The installation is exactly the same.

repo2docker/contentproviders/zenodo.py

@@ -20,6 +20,17 @@ class Zenodo(DoiProvider):
         # filepath (path to files in metadata), filename (path to filename in
         # metadata), download (path to file download URL), and type (path to item type in metadata)
         self.hosts = [
+            {
+                "hostname": [
+                    "https://sandbox.zenodo.org/record/",
+                    "http://sandbox.zenodo.org/record/",
+                ],
+                "api": "https://sandbox.zenodo.org/api/records/",
+                "filepath": "files",
+                "filename": "filename",
+                "download": "links.download",
+                "type": "metadata.upload_type",
+            },
             {
                 "hostname": ["https://zenodo.org/record/", "http://zenodo.org/record/"],
                 "api": "https://zenodo.org/api/records/",