Improve download tests

test/test_datasets_download.py

@@ -7,6 +7,7 @@
 from urllib.error import HTTPError, URLError
 from urllib.parse import urlparse
 from urllib.request import urlopen, Request
+import warnings
 
 import pytest
 
@@ -45,6 +46,31 @@ def inner_wrapper(request, *args, **kwargs):
 urlopen = limit_requests_per_time()(urlopen)
 
 
+def resolve_redirects(max_redirects=3):
+    def outer_wrapper(fn):
+        def inner_wrapper(request, *args, **kwargs):
+            url = initial_url = request.full_url if isinstance(request, Request) else request
+
+            for _ in range(max_redirects + 1):
+                response = fn(request, *args, **kwargs)
+
+                if response.url == url or response.url is None:
+                    if url != initial_url:
+                        warnings.warn(f"The URL {initial_url} ultimately redirects to {url}.")
+                    return response
+
+                url = response.url
+            else:
+                raise RecursionError(f"Request to {initial_url} exceeded {max_redirects} redirects.")
+
+        return inner_wrapper
+
+    return outer_wrapper
+
+
+urlopen = resolve_redirects()(urlopen)
+
+
 @contextlib.contextmanager
 def log_download_attempts(
     urls_and_md5s=None,
@@ -117,19 +143,22 @@ def assert_server_response_ok():
         raise AssertionError("The request timed out.") from error
     except HTTPError as error:
         raise AssertionError(f"The server returned {error.code}: {error.reason}.") from error
+    except RecursionError as error:
+        raise AssertionError(str(error)) from error
 
 
-def assert_url_is_accessible(url):
+def assert_url_is_accessible(url, timeout=5.0):
     request = Request(url, headers=dict(method="HEAD"))
     with assert_server_response_ok():
-        urlopen(request, timeout=5.0)
+        urlopen(request, timeout=timeout)
 
 
-def assert_file_downloads_correctly(url, md5):
+def assert_file_downloads_correctly(url, md5, timeout=5.0):
     with get_tmp_dir() as root:
         file = path.join(root, path.basename(url))
         with assert_server_response_ok():
-            with urlopen(url, timeout=5.0) as response, open(file, "wb") as fh:
+            with open(file, "wb") as fh:
+                response = urlopen(url, timeout=timeout)
                 fh.write(response.read())
 
         assert check_integrity(file, md5=md5), "The MD5 checksums mismatch"