Description: prevent dataset download during doc build. Guard with debian
 specific environment variable to avoid breaking the functionality.
Author: Mo Zhou <lumin@debian.org>
Forward: not-necessary
--- a/sklearn/datasets/_base.py
+++ b/sklearn/datasets/_base.py
@@ -1319,6 +1319,8 @@ def _fetch_remote(remote, dirname=None):
     file_path: str
         Full path of the created file.
     """
+    if int(os.getenv('DEBIAN_POLICY_SECTION_4_9_NO_NETWORK_ACCESS', '0')) > 0:
+        raise IOError('Debian Policy Section 4.9 prohibits network access during build')
 
     file_path = remote.filename if dirname is None else join(dirname, remote.filename)
     urlretrieve(remote.url, file_path)
--- a/sklearn/datasets/_openml.py
+++ b/sklearn/datasets/_openml.py
@@ -860,6 +860,9 @@ def fetch_openml(
     attribute `categories` of the `Bunch` instance. Instead, `"pandas"` returns
     a NumPy array were the categories are not encoded.
     """
+    if int(os.getenv('DEBIAN_POLICY_SECTION_4_9_NO_NETWORK_ACCESS', '0')) > 0:
+        raise TimeoutError('Debian Policy Section 4.9 prohibits network access during build')
+
     if cache is False:
         # no caching will be applied
         data_home = None
--- a/examples/applications/plot_stock_market.py
+++ b/examples/applications/plot_stock_market.py
@@ -97,6 +97,8 @@ for symbol in symbols:
         "https://raw.githubusercontent.com/scikit-learn/examples-data/"
         "master/financial-data/{}.csv"
     )
+    if int(os.getenv('DEBIAN_POLICY_SECTION_4_9_NO_NETWORK_ACCESS', '0')) > 0:
+        raise TimeoutError('Debian Policy Section 4.9 prohibits network access during build')
     quotes.append(pd.read_csv(url.format(symbol)))
 
 close_prices = np.vstack([q["close"] for q in quotes])
--- a/examples/applications/plot_out_of_core_classification.py
+++ b/examples/applications/plot_out_of_core_classification.py
@@ -168,7 +168,8 @@ def stream_reuters_documents(data_path=N
                 sys.stdout.write("\rdownloaded %s / %s" % (current_sz_mb, total_sz_mb))
 
         archive_path = data_path / ARCHIVE_FILENAME
-
+        if int(os.getenv('DEBIAN_POLICY_SECTION_4_9_NO_NETWORK_ACCESS', '0')) > 0:
+            raise TimeoutError('Debian Policy Section 4.9 prohibits network access during build')
         urlretrieve(DOWNLOAD_URL, filename=archive_path, reporthook=progress)
         if _not_in_sphinx():
             sys.stdout.write("\r")