Switch hub to use requests because of SSL (#25083)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25083

I missed this in the last PR

Test Plan: Imported from OSS

Differential Revision: D17005372

Pulled By: jamesr66a

fbshipit-source-id: 1200a6cd88fb9051aed8baf3162a9f8ffbf65189

.jenkins/caffe2/test.sh

@@ -106,6 +106,11 @@ if [[ "$BUILD_ENVIRONMENT" == *py3* ]]; then
   export LC_ALL=C.UTF-8
   export LANG=C.UTF-8
 fi
+
+if [[ "$BUILD_ENVIRONMENT" == *py2* ]]; then
+  pip install --user requests
+fi
+
 pip install --user pytest-sugar
 "$PYTHON" \
   -m pytest \
@@ -137,3 +142,4 @@ if [[ "$BUILD_ENVIRONMENT" == *onnx* ]]; then
   fi
   "$ROOT_DIR/scripts/onnx/test.sh"
 fi
+

.jenkins/pytorch/test.sh

@@ -56,6 +56,10 @@ if [[ "$BUILD_ENVIRONMENT" != *ppc64le* ]]; then
   pip_install --user mypy || true
 fi
 
+if [[ $PYTHON_VERSION == "2" ]]; then
+  pip_install --user requests
+fi
+
 # faulthandler become built-in since 3.3
 if [[ ! $(python -c "import sys; print(int(sys.version_info >= (3, 3)))") == "1" ]]; then
   pip_install --user faulthandler

setup.py

@@ -352,6 +352,9 @@ install_requires = []
 if sys.version_info <= (2, 7):
     install_requires += ['future']
 
+if sys.version_info[0] == 2:
+    install_requires += ['requests']
+
 missing_pydep = '''
 Missing build dependency: Unable to `import {importname}`.
 Please install it via `conda install {module}` or `pip install {module}`

torch/hub.py

@@ -4,7 +4,6 @@ import hashlib
 import os
 import re
 import shutil
-import ssl
 import sys
 import tempfile
 import torch
@@ -13,7 +12,7 @@ import zipfile
 
 if sys.version_info[0] == 2:
     from urlparse import urlparse
-    from urllib2 import urlopen  # noqa f811
+    import requests
 else:
     from urllib.request import urlopen
     from urllib.parse import urlparse  # noqa: F401
@@ -94,19 +93,12 @@ def _git_archive_link(repo_owner, repo_name, branch):
 
 def _download_archive_zip(url, filename):
     sys.stderr.write('Downloading: \"{}\" to {}\n'.format(url, filename))
-    # TODO: This is to get around CA issues on Python2, where urllib can't
-    # verify the cert from the github server. Another solution is to do:
-    #
-    # import certifi
-    # ...
-    # urlopen(url, cafile=certifi.where())
-    #
-    # But it requires adding a dependency on the `certifi` package
+    # We use a different API for python2 since urllib(2) doesn't recognize the CA
+    # certificates in older Python
     if sys.version_info[0] == 2:
-        context = ssl._create_unverified_context()
+        response = requests.get(url, stream=True).raw
     else:
-        context = None
-    response = urlopen(url, context=context)
+        response = urlopen(url)
     with open(filename, 'wb') as f:
         while True:
             data = response.read(READ_DATA_CHUNK)
@@ -382,14 +374,24 @@ def load(github, model, *args, **kwargs):
 
 def _download_url_to_file(url, dst, hash_prefix, progress):
     file_size = None
-    u = urlopen(url)
-    meta = u.info()
-    if hasattr(meta, 'getheaders'):
-        content_length = meta.getheaders("Content-Length")
+    # We use a different API for python2 since urllib(2) doesn't recognize the CA
+    # certificates in older Python
+    if sys.version_info[0] == 2:
+        response = requests.get(url, stream=True)
+
+        content_length = response.headers['Content-Length']
+        file_size = content_length
+        u = response.raw
     else:
-        content_length = meta.get_all("Content-Length")
-    if content_length is not None and len(content_length) > 0:
-        file_size = int(content_length[0])
+        u = urlopen(url)
+
+        meta = u.info()
+        if hasattr(meta, 'getheaders'):
+            content_length = meta.getheaders("Content-Length")
+        else:
+            content_length = meta.get_all("Content-Length")
+        if content_length is not None and len(content_length) > 0:
+            file_size = int(content_length[0])
 
     # We deliberately save it in a temp file and move it after
     # download is complete. This prevents a local working checkpoint