staticx: Use importlib.resources over pkg_resources for asset access

pkg_resources is deprecated:
https://setuptools.pypa.io/en/latest/pkg_resources.html

This prefers importlib.metadata (introduced in Python 3.8) and uses the
backport importlib_metadata for Python 3.7 (to be removed in #264).

This instead uses importlib.resources.files() (introduced in Python 3.9)
and uses the backport importlib_resources for Python 3.7-3.8 (to be
removed in #264, #265).

This was chosen over the alternative of using the deprecated (as of
Python 3.11) function importlib.resources.open_binary() (introduced in
Python 3.7), as it seems simpler.

pyproject.toml

@@ -26,6 +26,8 @@ dependencies = [
     "pyelftools",
     # TODO(#264): Remove when Python 3.7 support is removed.
     "importlib_metadata; python_version<'3.8'",
+    # TODO(#265): Remove when Python 3.8 support is removed.
+    "importlib_resources; python_version<'3.9'",
 ]
 description = "Build static self-extracting app from dynamic executable"
 license = {file = "LICENSE.txt"}

staticx/assets.py

@@ -1,11 +1,19 @@
-import pkg_resources
+import sys
 from .utils import copy_fileobj_to_tempfile
 
+# TODO(#265): Remove backport when Python 3.8 support is removed.
+# importlib.resources.files() was added in Python 3.9.
+if sys.version_info >= (3, 9):
+    import importlib.resources as importlib_resources
+else:
+    import importlib_resources  # backport
+
+
 def locate_asset(name, debug):
     mode = 'debug' if debug else 'release'
     path = '/'.join(('assets', mode, name))
     try:
-        return pkg_resources.resource_stream(__name__, path)
+        return importlib_resources.files("staticx").joinpath(path).open("rb")
     except FileNotFoundError:
         raise KeyError(f"Asset not found: {name!r} (mode={mode!r})")
 

staticx/version.py

@@ -62,7 +62,7 @@ def get_version():
     # Otherwise, we're either installed (e.g. via pip), or running from
     # an 'sdist' source distribution, and have a local PKG_INFO file.
 
-    # TODO(#242): Remove backport when Python 3.7 support is removed.
+    # TODO(#264): Remove backport when Python 3.7 support is removed.
     if sys.version_info >= (3, 8):
         import importlib.metadata as importlib_metadata
     else: