Add pre-commit: pretter, black, pyupgrade, and misc

.flake8

@@ -0,0 +1,16 @@
+# flake8 is a Python linting tool run by pre-commit as declared by our
+# pre-commit-config.yaml file.
+#
+# This configuration is compatible with the autoformatter tool black, and
+# further relaxed to not bug us with too small details.
+#
+# flake8 configuration reference:
+# https://flake8.pycqa.org/en/latest/user/configuration.html
+#
+[flake8]
+max-line-length = 88
+extend-ignore = C, E, W
+
+# Adjustments to linting the binderhub repo
+builtins = c, load_subconfig
+exclude = versioneer.py,binderhub/_version.py

.pre-commit-config.yaml

@@ -0,0 +1,65 @@
+# pre-commit is a tool to perform a predefined set of tasks manually and/or
+# automatically before git commits are made.
+#
+# Config reference: https://pre-commit.com/#pre-commit-configyaml---top-level
+#
+# Common tasks
+#
+# - Run on all files:   pre-commit run --all-files
+# - Register git hooks: pre-commit install --install-hooks
+#
+repos:
+  # Autoformat: Python code, syntax patterns are modernized
+  - repo: https://github.com/asottile/pyupgrade
+    rev: v2.31.0
+    hooks:
+      - id: pyupgrade
+        args:
+          - --py37-plus
+
+  # Autoformat: Python code
+  - repo: https://github.com/psf/black
+    rev: 22.1.0
+    hooks:
+      - id: black
+        args: [--target-version=py37]
+
+  # Autoformat: Python code
+  - repo: https://github.com/asottile/reorder_python_imports
+    rev: v3.0.1
+    hooks:
+      - id: reorder-python-imports
+
+  # Autoformat: js, html, markdown, yaml, json
+  - repo: https://github.com/pre-commit/mirrors-prettier
+    rev: v2.6.1
+    hooks:
+      - id: prettier
+        exclude_types:
+          # These are excluded initially as pre-commit was added but can
+          # absolutely be enabled later. If so, we should consider having a
+          # separate run of pre-commit where we configure a line spacing of 4
+          # for these file formats.
+          - html
+          - javascript
+          - css
+
+  # Misc autoformatting and linting
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.1.0
+    hooks:
+      - id: end-of-file-fixer
+        exclude_types: [svg]
+      - id: check-case-conflict
+      - id: check-executables-have-shebangs
+      - id: requirements-txt-fixer
+
+  # Lint: Python code
+  - repo: https://github.com/PyCQA/flake8
+    rev: "4.0.1"
+    hooks:
+      - id: flake8
+
+# versioneer.py is excluded for being an imported dependency we opt to not
+# modify ourselves. This is also set in .flake8 for consistency.
+exclude: versioneer.py|binderhub/_version.py

.prettierignore

@@ -0,0 +1,2 @@
+helm-chart/binderhub/templates/
+http-record.doi.org.json

binderhub/launcher.py

@@ -243,7 +243,7 @@ def _cancel_ready_event(f=None):
                 else:
                     ready_event_future.cancel()
         try:
-            resp = await self.api_request(
+            await self.api_request(
                 'users/{}/servers/{}'.format(escaped_username, server_name),
                 method='POST',
                 body=json.dumps(data).encode('utf8'),