Add linting configuration

.flake8

@@ -0,0 +1,15 @@
+[flake8]
+max-line-length = 88
+ignore = E501, E203, W503
+per-file-ignores = __init__.py:F401
+exclude =
+    .git
+    __pycache__
+    dist
+    vendor
+    .venv
+    .tox
+    .pytest_cache
+    .github
+    _legacy
+    _internal

.pre-commit-config.yaml

@@ -0,0 +1,25 @@
+repos:
+  - repo: https://github.com/psf/black
+    rev: 19.10b0
+    hooks:
+      - id: black
+        exclude: &exclude |
+          (?x)(
+              ^src/gnmi/proto/_internal/.*
+              | ^src/gnmi/proto/_legacy/.*
+          )
+
+  - repo: https://gitlab.com/pycqa/flake8
+    rev: 3.8.3
+    hooks:
+      - id: flake8
+        exclude: *exclude
+
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v3.1.0
+    hooks:
+      - id: trailing-whitespace
+        exclude: *exclude
+      - id: end-of-file-fixer
+        exclude: *exclude
+      - id: debug-statements