Fix Docs CI (ethereum#2175)

* Fix docs CI runs

* Cache doc dependencies

* Increase resource class

.circleci/config.yml

@@ -113,15 +113,34 @@ windows-wheel-steps:
         - .tox
       key: cache-v1-{{ arch }}-{{ .Environment.CIRCLE_JOB }}-{{ checksum "setup.py" }}-{{ checksum "tox.ini" }}
 
+
 docs: &docs
-  docker:
-    - image: common
+  working_directory: ~/repo
   steps:
+    - checkout
+    - restore_cache:
+        keys:
+          - cache-v1-{{ arch }}-{{ .Environment.CIRCLE_JOB }}-{{ checksum "setup.py" }}-{{ checksum "tox.ini" }}
+    - run:
+        name: install dependencies
+        command: |
+          python -m pip install --upgrade pip
+          python -m pip install tox
     - run:
         name: install latexpdf dependencies
         command: |
           sudo apt-get update
           sudo apt-get install latexmk tex-gyre texlive-fonts-extra
+    - run:
+        name: run tox
+        command: python -m tox run -r
+    - save_cache:
+        paths:
+          - .tox
+          - ~/.cache/pip
+          - ~/.local
+        key: cache-v1-{{ arch }}-{{ .Environment.CIRCLE_JOB }}-{{ checksum "setup.py" }}-{{ checksum "tox.ini" }}
+  resource_class: xlarge
 
 jobs:
   docs:

docs/guides/understanding_the_mining_process.rst

@@ -386,7 +386,8 @@ zero value transfer transaction.
   ...     block.number,
   ...     block.header.mining_hash,
   ...     block.header.difficulty,
-  ... )  # doctest: +SKIP (takes too long for doctest to process)
+  ... )  # doctest: +SKIP
+  ... # (takes too long for doctest to process)
 
   >>> chain.mine_block(mix_hash=mix_hash, nonce=nonce)  # doctest: +SKIP
   <ByzantiumBlock(#Block #1-0xe372..385c)>

newsfragments/2175.internal.rst

@@ -0,0 +1 @@
+Ensure docs build on CI is running.