Add a nox session for running xdoctest

- add a session "doctests" to nox
- run it as a pre-commit hook

.pre-commit-config.yaml

@@ -3,6 +3,12 @@ fail_fast: true
 repos:
 - repo: local
   hooks:
+  - id: doctests
+    name: Run the xdoctests in the source files
+    entry: poetry run nox -s doctests --
+    language: system
+    stages: [commit, merge-commit]
+    types: [python]
   - id: fix-branch-references
     name: Check for wrong branch references
     entry: poetry run nox -s fix-branch-references --

noxfile.py

@@ -4,6 +4,8 @@ Nox provides the following tasks:
 
 - "init-project": install the pre-commit hooks
 
+- "doctests": run the xdoctests in the source files
+
 - "fix-branch-references": adjusts links with git branch references in
   various files (e.g., Mardown or notebooks)
 
@@ -22,6 +24,11 @@ import nox
 
 REPOSITORY = "webartifex/intro-to-python"
 
+SRC_LOCATIONS = (
+    "02_functions/sample_module.py",
+    "11_classes/sample_package",
+)
+
 # Use a unified .cache/ folder for all develop tools.
 nox.options.envdir = ".cache/nox"
 
@@ -45,6 +52,13 @@ def init_project(session):
     )
 
 
+@nox.session(venv_backend="none")
+def doctests(session):
+    """Run the xdoctests in the source files."""
+    for location in SRC_LOCATIONS:
+        session.run("poetry", "run", "xdoctest", "--silent", location)
+
+
 @nox.session(name="fix-branch-references", venv_backend="none")
 def fix_branch_references(_session):
     """Change git branch references.