[3.x] Fix pkg_resources deprecation - use importlib.metadata when available (#726)3.x

* Fix pkg_resources deprecation - use importlib.metadata when available

Usage of pkg_resources now emits a deprecation warning. It is also quite
slow (just importing it).

Use importlib.metadata instead which is the recommended alternative.

* Use importlib-metadata backport for older pythons

* Removed setuptools as a run-time dependency

---------

Co-authored-by: Alex Grönholm <alex.gronholm@nextday.fi>

3 files changed, 25 insertions, 10 deletions

diff --git a/apscheduler/__init__.py b/apscheduler/__init__.py
index 968169a..651aba4 100644
--- a/apscheduler/__init__.py
+++ b/apscheduler/__init__.py
@@ -1,10 +1,15 @@
-from pkg_resources import get_distribution, DistributionNotFound
+import sys
+if sys.version_info >= (3, 8):
+    import importlib.metadata as importlib_metadata
+else:
+    import importlib_metadata
+
 
 try:
-    release = get_distribution('APScheduler').version.split('-')[0]
-except DistributionNotFound:
+    release = importlib_metadata.version('APScheduler').split('-')[0]
+except importlib_metadata.PackageNotFoundError:
     release = '3.5.0'
 
 version_info = tuple(int(x) if x.isdigit() else x for x in release.split('.'))
 version = __version__ = '.'.join(str(x) for x in version_info[:3])
-del get_distribution, DistributionNotFound
+del sys, importlib_metadata
diff --git a/apscheduler/schedulers/base.py b/apscheduler/schedulers/base.py
index 444de8e..3ce2bfc 100644
--- a/apscheduler/schedulers/base.py
+++ b/apscheduler/schedulers/base.py
@@ -7,7 +7,6 @@ from logging import getLogger
 import warnings
 import sys
 
-from pkg_resources import iter_entry_points
 from tzlocal import get_localzone
 import six
 
@@ -31,6 +30,11 @@ try:
 except ImportError:
     from collections import MutableMapping
 
+try:
+    from importlib.metadata import entry_points
+except ModuleNotFoundError:
+    from importlib_metadata import entry_points
+
 #: constant indicating a scheduler's stopped state
 STATE_STOPPED = 0
 #: constant indicating a scheduler's running state (started and processing jobs)
@@ -62,12 +66,18 @@ class BaseScheduler(six.with_metaclass(ABCMeta)):
 
     .. seealso:: :ref:`scheduler-config`
     """
+    # The `group=...` API is only available in the backport, used in <=3.7, and in std>=3.10.
+    if (3, 8) <= sys.version_info <= (3, 9):
+        _trigger_plugins = {ep.name: ep for ep in entry_points()['apscheduler.triggers']}
+        _executor_plugins = {ep.name: ep for ep in entry_points()['apscheduler.executors']}
+        _jobstore_plugins = {ep.name: ep for ep in entry_points()['apscheduler.jobstores']}
+    else:
+        _trigger_plugins = {ep.name: ep for ep in entry_points(group='apscheduler.triggers')}
+        _executor_plugins = {ep.name: ep for ep in entry_points(group='apscheduler.executors')}
+        _jobstore_plugins = {ep.name: ep for ep in entry_points(group='apscheduler.jobstores')}
 
-    _trigger_plugins = dict((ep.name, ep) for ep in iter_entry_points('apscheduler.triggers'))
     _trigger_classes = {}
-    _executor_plugins = dict((ep.name, ep) for ep in iter_entry_points('apscheduler.executors'))
     _executor_classes = {}
-    _jobstore_plugins = dict((ep.name, ep) for ep in iter_entry_points('apscheduler.jobstores'))
     _jobstore_classes = {}
 
     #
diff --git a/setup.py b/setup.py
index 3b452aa..cd93e10 100644
--- a/setup.py
+++ b/setup.py
@@ -39,10 +39,10 @@ setup(
         'setuptools_scm'
     ],
     install_requires=[
-        'setuptools >= 0.7',
         'six >= 1.4.0',
         'pytz',
-        'tzlocal >= 2.0, != 3.*'
+        'tzlocal >= 2.0, != 3.*',
+        'importlib-metadata >= 3.6.0; python_version < "3.8"',
     ],
     extras_require={
         'gevent': ['gevent'],