Move from pkg resources to importlib (#172)

* move to importlib

* install/use importlib_metadata for py < 3.8

---------

Co-authored-by: Nick Krabbenhoeft <nickkrabbenhoeft@nypl.org>

Author: kba

bagit.py

@@ -21,7 +21,10 @@
 from functools import partial
 from os.path import abspath, isdir, isfile, join
 
-from pkg_resources import DistributionNotFound, get_distribution
+try:
+    from importlib.metadata import version
+except ImportError:
+    from importlib_metadata import version
 
 try:
     from urllib.parse import urlparse
@@ -48,9 +51,8 @@ def find_locale_dir():
 
 LOGGER = logging.getLogger(MODULE_NAME)
 
-try:
-    VERSION = get_distribution(MODULE_NAME).version
-except DistributionNotFound:
+VERSION = version(MODULE_NAME)
+if not VERSION:
     VERSION = "0.0.dev0"
 
 PROJECT_URL = "https://github.com/LibraryOfCongress/bagit-python"

setup.py

@@ -62,6 +62,7 @@ def get_message_catalogs():
     platforms=["POSIX"],
     test_suite="test",
     setup_requires=["setuptools_scm"],
+    install_requires=["importlib_metadata ; python_version < '3.8'"],
     tests_require=tests_require,
     classifiers=[
         "License :: Public Domain",