Relax minimum version of requests to allow 2.21.0 (#2914)

Author: nfelt

.travis.yml

@@ -57,6 +57,7 @@ install:
   - pip install grpcio-testing==1.24.3
   - pip install 'google-auth >= 1.6.3, < 2'
   - pip install 'google-auth-oauthlib >= 0.4.1, < 0.5'
+  - pip install requests==2.21.0
   - yarn install --ignore-engines
   # Uninstall older Travis numpy to avoid upgrade-in-place issues.
   - pip uninstall -y numpy

tensorboard/pip_package/setup.py

@@ -32,7 +32,7 @@
     'markdown >= 2.6.8',
     'numpy >= 1.12.0',
     'protobuf >= 3.6.0',
-    'requests >= 2.22.0, < 3',
+    'requests >= 2.21.0, < 3',
     'setuptools >= 41.0.0',
     'six >= 1.10.0',
     'werkzeug >= 0.11.15',