Reformat using black (#281)

The Ray main repo is using black, so we may want to do the same.

.flake8

@@ -0,0 +1,40 @@
+[flake8]
+max-line-length = 88
+inline-quotes = "
+ignore =
+  C408
+  C417
+  E121
+  E123
+  E126
+  E203
+  E226
+  E24
+  E704
+  W503
+  W504
+  W605
+  I
+  N
+  B001
+  B002
+  B003
+  B004
+  B005
+  B007
+  B008
+  B009
+  B010
+  B011
+  B012
+  B013
+  B014
+  B015
+  B016
+  B017
+avoid-escape = no
+# Error E731 is ignored because of the migration from YAPF to Black.
+# See https://github.com/ray-project/ray/issues/21315 for more information.
+per-file-ignores =
+    rllib/evaluation/worker_set.py:E731
+    rllib/evaluation/sampler.py:E731

.github/workflows/test.yaml

@@ -20,12 +20,13 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         python -m pip install codecov
-        python -m pip install -U yapf==0.23.0 flake8==3.7.7 flake8-comprehensions flake8-quotes==2.0.0
+        if [ -f requirements/lint-requirements.txt ]; then python -m pip install -r requirements/lint-requirements.txt; fi
     - name: Print environment info
       run: |
         ./xgboost_ray/tests/env_info.sh
     - name: Run format script
       run: |
+        ls -alp
         ./format.sh --all
 
   test_linux_ray_master:
@@ -52,7 +53,7 @@ jobs:
         python -m pip install --upgrade pip
         python -m pip install codecov
         python -m pip install -U ${{ matrix.ray-wheel }}
-        if [ -f requirements-test.txt ]; then python -m pip install -r requirements-test.txt; fi
+        if [ -f requirements/test-requirements.txt ]; then python -m pip install -r requirements/test-requirements.txt; fi
     - name: Install package
       run: |
         python -m pip install -e .
@@ -89,7 +90,7 @@ jobs:
         python -m pip install --upgrade pip
         python -m pip install codecov
         python -m pip install -U ray
-        if [ -f requirements-test.txt ]; then python -m pip install  -r requirements-test.txt; fi
+        if [ -f requirements/test-requirements.txt ]; then python -m pip install -r requirements/test-requirements.txt; fi
     - name: Install package
       run: |
         python -m pip install -e .
@@ -128,7 +129,7 @@ jobs:
         python -m pip install --upgrade pip
         python -m pip install codecov
         python -m pip install -U ray
-        if [ -f requirements-test.txt ]; then python -m pip install -r requirements-test.txt; fi
+        if [ -f requirements/test-requirements.txt ]; then python -m pip install -r requirements/test-requirements.txt; fi
     - name: Uninstall unavailable dependencies
       # Disables modin and Ray Tune (via tabulate)
       run: |
@@ -179,7 +180,7 @@ jobs:
         python -m pip install --upgrade pip
         python -m pip install codecov
         python -m pip install -U ${{ matrix.ray-wheel }}
-        if [ -f requirements-test.txt ]; then python -m pip install -r requirements-test.txt; fi
+        if [ -f requirements/test-requirements.txt ]; then python -m pip install -r requirements/test-requirements.txt; fi
     - name: Install Ubuntu system dependencies
       run: |
         sudo apt-get install -y --no-install-recommends ninja-build
@@ -234,7 +235,7 @@ jobs:
         python -m pip install --upgrade pip
         python -m pip install codecov
         python -m pip install -U ray
-        if [ -f requirements-test.txt ]; then python -m pip install  -r requirements-test.txt; fi
+        if [ -f requirements/test-requirements.txt ]; then python -m pip install -r requirements/test-requirements.txt; fi
     - name: Install package
       run: |
         python -m pip install -e .