Update minimum requests version to 2.3

There are a number of features and tests that don't pass with requests
versions older than 2.3. This version was released in May 2014, so I
think we should be safe by now.

Closes: #89

.circleci/config.yml

@@ -62,6 +62,37 @@ jobs:
             source venv/bin/activate
             tox -e py27
 
+  oldest:
+    docker:
+      - image: circleci/python:3.6
+
+    steps:
+      - checkout
+
+      - restore_cache:
+          keys:
+            - oldest-dependencies-{{ checksum "requirements.txt" }}-{{ checksum "test-requirements.txt" }}
+
+      - run:
+          name: install dependencies
+          command: |
+            python3 -m venv venv
+            source venv/bin/activate
+            pip3 install tox
+            tox -e oldest-requirements --notest
+
+      - save_cache:
+          paths:
+            - ./venv
+            - .tox/py36
+          key: oldest-dependencies-{{ checksum "requirements.txt" }}-{{ checksum "test-requirements.txt" }}
+
+      - run:
+          name: run tests
+          command: |
+            source venv/bin/activate
+            tox -e py36
+
   pypi:
     docker:
       - image: circleci/python:3.6
@@ -92,10 +123,16 @@ workflows:
             tags:
               only: /^\d+\.\d+\.\d+$/
 
+      - oldest:
+          filters:
+            tags:
+              only: /^\d+\.\d+\.\d+$/
+
       - pypi:
           requires:
             - py27
             - py36
+            - oldest
           filters:
             branches:
               ignore: /.*/

.tox.oldest.txt

@@ -0,0 +1 @@
+requests==2.0.0

releasenotes/notes/Bump-minimum-requests-2.3-70fd287f6ea1a12e.yaml

@@ -0,0 +1,10 @@
+---
+prelude: >
+  Increase the minimum required requests version to 2.3
+critical:
+  - |
+    The minimum version of requests has been increase to 2.3. This simply
+    ensures that all documented features of requests-mock are actually
+    available. This version of requests is still quite old and if this is an
+    issue you should either pin requests-mock to <1.6 or preferably update
+    requests.

requirements.txt

@@ -1,2 +1,2 @@
-requests>=1.1
+requests>=2.3
 six

tox.ini

@@ -30,10 +30,14 @@ deps =
     coverage
     {[testenv]deps}
 
-[testenv:requests123]
+[testenv:oldest-requirements]
+install_command = pip install -U {opts} -c {toxinidir}/.tox.oldest.txt {packages}
 commands =
-    {envbindir}/pip install "requests==1.2.3"
     python setup.py testr --testr-args='{posargs}'
+deps =
+    -r{toxinidir}/test-requirements.txt
+    -c{toxinidir}/.tox.oldest.txt
+    pbr
 
 [testenv:doctest]
 # note this only works under python 3 because of unicode literals