Add py.typed file to package for PEP-561 compliance

Per PEP-561, packages that include type information that can be consumed
by other libraries should distribute a py.typed file. This tells mypy
and other tools to use type information shipped with the library.

This requires moving distro from a single module file to a package so
that it can ship data files. The original distro.py was not altered.
Only the __init__.py and __main__.py were added to facilitate being used
as a packages. By keeping distro.py unaltered, this allows projects to
continue to vendor the file into their project without as before without
any modifications.

For details on PEP-561, see:
https://www.python.org/dev/peps/pep-0561/

For details on mypy using py.typed, see:
https://mypy.readthedocs.io/en/stable/installed_packages.html#creating-pep-561-compatible-packages

README.md

@@ -36,6 +36,20 @@ Installation of the latest development version:
 pip install https://github.com/python-distro/distro/archive/master.tar.gz
 ```
 
+To use as a standalone script, download `distro.py` directly:
+
+```shell
+curl -O https://raw.githubusercontent.com/python-distro/distro/master/src/distro/distro.py
+python distro.py
+```
+
+``distro`` is safe to vendor within projects that do not wish to add
+dependencies.
+
+```shell
+cd myproject
+curl -O https://raw.githubusercontent.com/python-distro/distro/master/src/distro/distro.py
+```
 
 ## Usage
 

setup.cfg

@@ -30,12 +30,17 @@ classifiers =
     Topic :: System :: Operating System
 
 [options]
-py_modules = distro
+package_dir =
+    = src
+packages = distro
 python_requires = >=3.6
 
+[options.package_data]
+* = py.typed
+
 [options.entry_points]
 console_scripts =
-    distro = distro:main
+    distro = distro.distro:main
 
 [flake8]
 max-line-length = 88

src/distro/__init__.py

@@ -0,0 +1,54 @@
+from .distro import (
+    NORMALIZED_DISTRO_ID,
+    NORMALIZED_LSB_ID,
+    NORMALIZED_OS_ID,
+    LinuxDistribution,
+    __version__,
+    build_number,
+    codename,
+    distro_release_attr,
+    distro_release_info,
+    id,
+    info,
+    like,
+    linux_distribution,
+    lsb_release_attr,
+    lsb_release_info,
+    major_version,
+    minor_version,
+    name,
+    os_release_attr,
+    os_release_info,
+    uname_attr,
+    uname_info,
+    version,
+    version_parts,
+)
+
+__all__ = [
+    "NORMALIZED_DISTRO_ID",
+    "NORMALIZED_LSB_ID",
+    "NORMALIZED_OS_ID",
+    "LinuxDistribution",
+    "build_number",
+    "codename",
+    "distro_release_attr",
+    "distro_release_info",
+    "id",
+    "info",
+    "like",
+    "linux_distribution",
+    "lsb_release_attr",
+    "lsb_release_info",
+    "major_version",
+    "minor_version",
+    "name",
+    "os_release_attr",
+    "os_release_info",
+    "uname_attr",
+    "uname_info",
+    "version",
+    "version_parts",
+]
+
+__version__ = __version__

src/distro/__main__.py

@@ -0,0 +1,4 @@
+from .distro import main
+
+if __name__ == "__main__":
+    main()

tests/test_distro.py

@@ -33,7 +33,7 @@
 
 IS_LINUX = sys.platform.startswith("linux")
 if IS_LINUX:
-    import distro
+    from distro import distro
 
     RELATIVE_UNIXCONFDIR = distro._UNIXCONFDIR[1:]
     RELATIVE_UNIXUSRLIBDIR = distro._UNIXUSRLIBDIR[1:]