Install a patched version of pytest on CircleCI (#477)

Summary:
Pull Request resolved: #477

As titled. Currently pytest's `import-mode=importlib` option does not add the test file to `sys.module`, which can break some of the use cases. While [the community has came up with a fix](pytest-dev/pytest#7870), it's not yet clear when the particular PR will be merged and added to the latest pytest. So in the meanwhile, we could download and use the patched version by directly from the PR so we are not blocked.

Reviewed By: ericlippert

Differential Revision: D25480894

fbshipit-source-id: 5eddce784a247f68ebcaa5ae85065220f65d847a

Author: horizon-blue

.circleci/config.yml

@@ -31,6 +31,14 @@ commands:
           name: "Install beanmachine"
           command: sudo pip install --progress-bar off -v .
 
+  pip_install_pytest_patch:
+    steps:
+      - run:
+          name: "Install a patched pytest version from PR (pytest-dev/pytest#7870)"
+          command: >
+            sudo pip install --progress-bar off
+            git+https://github.com/pytest-dev/pytest.git@refs/pull/7870/head
+
   apt_get_install_deps:
     description: "Install beanmachine graph dependencies via apt-get"
     steps:
@@ -113,6 +121,7 @@ jobs:
       - pip_install_deps
       - checkout
       - dev_install
+      - pip_install_pytest_patch
       - dev_unit_tests
 
   user_par_install_test_py37_pip:
@@ -123,6 +132,7 @@ jobs:
       - pip_install_deps
       - checkout
       - user_install
+      - pip_install_pytest_patch
       - user_par_unit_tests
 
   lint_py37_pip:
@@ -143,6 +153,7 @@ jobs:
       - pip_install_deps
       - checkout
       - user_install
+      - pip_install_pytest_patch
       - nightly_tests