docs: avoid pkg_resources in Sphinx config

docs/conf.py

@@ -24,10 +24,10 @@
 
 from __future__ import print_function
 
+import ast
+import os
 import sys
 
-from pkg_resources import get_distribution
-
 _html_theme = "sphinx_rtd_theme"
 _html_theme_path = []
 try:
@@ -37,6 +37,23 @@
     print("Template {0} not found, pip install it", file=sys.stderr)
     _html_theme = "default"
 
+
+def _read_version():
+    """Read the generated package version without packaging helpers."""
+    version_path = os.path.join(
+        os.path.dirname(__file__), '..', 'dictdiffer', 'version.py'
+    )
+    with open(version_path, encoding='utf-8') as version_file:
+        module = ast.parse(version_file.read(), filename=version_path)
+
+    for node in module.body:
+        if isinstance(node, ast.Assign):
+            for target in node.targets:
+                if isinstance(target, ast.Name) and target.id == '__version__':
+                    return ast.literal_eval(node.value)
+
+    raise RuntimeError('Unable to read dictdiffer version')
+
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
@@ -81,7 +98,7 @@
 # built documents.
 #
 # The short X.Y version.
-version = get_distribution('dictdiffer').version
+version = _read_version()
 
 # The full version, including alpha/beta/rc tags.
 release = version