Don't install repository tools/ directory as a package

Fixed issue in the 1.4.0 packaging where the repository's internal
``tools/`` directory was detected by setuptools package discovery and
installed as a top-level ``tools`` package into site-packages, shadowing
unrelated ``tools`` packages belonging to other applications.  Package
discovery is now limited to the ``mako`` package explicitly, matching
what Alembic does, and the empty ``tools/__init__.py`` is removed so
that ``tools`` is a namespace package as it is in SQLAlchemy and
Alembic; ``noxfile.py`` continues to import from it, and ``tools/``
remains part of the sdist so that nox can run there.

Fixes: #438
Change-Id: I15e4719e40b493ef7da94f3e94a2fbe315fc41dc

Author: zzzeek

doc/build/unreleased/438.rst

@@ -0,0 +1,9 @@
+.. change::
+    :tags: bug, installation
+    :tickets: 438
+
+    Fixed issue in the 1.4.0 packaging where the repository's internal
+    ``tools/`` directory was detected by setuptools package discovery and
+    installed as a top-level ``tools`` package into site-packages, shadowing
+    unrelated ``tools`` packages belonging to other applications.  Package
+    discovery is now limited to the ``mako`` package explicitly.

pyproject.toml

@@ -101,6 +101,7 @@ zip-safe = false
 include-package-data = false
 
 [tool.setuptools.packages.find]
+include = ["mako*"]
 exclude = [
     "test*",
     "examples*",