Use stdlib instead of pytz on Python >= 3.9

Python 3.9 introduced the zoneinfo module, which provides the only
feature we used pytz for (getting a datetime.tzinfo object from
an IANA timezone id); so let's use it instead of a third-party
dependency.

plugins/Time/plugin.py

@@ -71,11 +71,6 @@ try:
 except ImportError:
     tzlocal = None
 
-try:
-    import pytz
-except ImportError:
-    pytz = None
-
 class Time(callbacks.Plugin):
     """This plugin allows you to use different time-related functions."""
     @internationalizeDocstring
@@ -200,19 +195,22 @@ class Time(callbacks.Plugin):
 
     @internationalizeDocstring
     def tztime(self, irc, msg, args, timezone):
-        """<region>/<city>
+        """<region>/<city> (or <region>/<state>/<city>)
 
         Takes a city and its region, and returns its local time. This
         command uses the IANA Time Zone Database."""
-        if pytz is None:
-            irc.error(_('Python-tz is required by the command, but is not '
-                        'installed on this computer.'), Raise=True)
         try:
-            timezone = pytz.timezone(timezone)
-        except pytz.UnknownTimeZoneError:
-            irc.error(_('Unknown timezone'), Raise=True)
-        format = self.registryValue("format", msg.channel, irc.network)
-        irc.reply(datetime.now(timezone).strftime(format))
+            timezone = utils.time.iana_timezone(timezone)
+        except utils.time.UnknownTimeZone:
+            irc.error(_('Unknown timezone'))
+        except utils.time.MissingTimezoneLibrary:
+            irc.error(_('Python-tz is required by the command, but is not '
+                        'installed on this computer.'))
+        except utils.time.UnknownTimeZone as e:
+            irc.error(e.args[0])
+        else:
+            format = self.registryValue("format", msg.channel, irc.network)
+            irc.reply(datetime.now(timezone).strftime(format))
     tztime = wrap(tztime, ['text'])
 
     def ddate(self, irc, msg, args, year=None, month=None, day=None):

plugins/Time/test.py

@@ -28,14 +28,18 @@
 # POSSIBILITY OF SUCH DAMAGE.
 ###
 
+import sys
 from supybot.test import *
 
-try:
-    import pytz
-except ImportError:
-    has_pytz = False
+if sys.version_info >= (3, 9):
+    has_tz_lib = True
 else:
-    has_pytz = True
+    try:
+        import pytz
+    except ImportError:
+        has_tz_lib = False
+    else:
+        has_tz_lib = True
 
 try:
     import dateutil
@@ -88,9 +92,10 @@ class TimeTestCase(PluginTestCase):
         self.assertNotError('ctime')
         self.assertNotError('time %Y')
 
-    @skipIf(not has_pytz, 'pytz is missing')
+    @skipIf(not has_tz_lib, 'python version is older than 3.9 and pytz is missing')
     def testTztime(self):
         self.assertNotError('tztime Europe/Paris')
+        self.assertNotError('tztime America/Indiana/Knox')
         self.assertError('tztime Europe/Gniarf')
 
     @skipIf(not has_dateutil, 'python-dateutil is missing')

requirements.txt

@@ -1,6 +1,6 @@
 setuptools
 chardet
-pytz
+pytz;python_version<'3.9'
 python-dateutil
 python-gnupg
 feedparser

src/utils/__init__.py

@@ -63,6 +63,6 @@ internationalization = builtins.get('supybotInternationalization', None)
 # These imports need to happen below the block above, so things get put into
 # __builtins__ appropriately.
 from .gen import *
-from . import crypt, error, file, iter, net, python, seq, str, transaction, web
+from . import crypt, error, file, iter, net, python, seq, str, time, transaction, web
 
 # vim:set shiftwidth=4 softtabstop=4 expandtab textwidth=79:

src/utils/time.py

@@ -0,0 +1,73 @@
+###
+# Copyright (c) 2021, Valentin Lorentz
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+#   * Redistributions of source code must retain the above copyright notice,
+#     this list of conditions, and the following disclaimer.
+#   * Redistributions in binary form must reproduce the above copyright notice,
+#     this list of conditions, and the following disclaimer in the
+#     documentation and/or other materials provided with the distribution.
+#   * Neither the name of the author of this software nor the name of
+#     contributors to this software may be used to endorse or promote products
+#     derived from this software without specific prior written consent.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+
+###
+
+import re
+import sys
+
+if sys.version_info >= (3, 9):
+    import zoneinfo
+else:
+    zoneinfo = None
+
+try:
+    import pytz
+except ImportError:
+    pytz = None
+
+_IANA_TZ_RE = re.compile("([\w_-]+/)+[\w_-]+")
+
+class TimezoneException(Exception):
+    pass
+
+class MissingTimezoneLibrary(TimezoneException):
+    pass
+
+class UnknownTimeZone(TimezoneException):
+    pass
+
+def iana_timezone(name):
+    if not _IANA_TZ_RE.match(name):
+        raise UnknownTimeZone(name)
+
+    if zoneinfo:
+        try:
+            return zoneinfo.ZoneInfo(name)
+        except zoneinfo.ZoneInfoNotFoundError as e:
+            raise UnknownTimeZone(e.args[0]) from None
+    elif pytz:
+        try:
+            timezone = pytz.timezone(name)
+        except pytz.UnknownTimeZoneError as e:
+            raise UnknownTimeZone(e.args[0]) from None
+    else:
+        raise MissingTimezoneLibrary(
+            "Could not find a timezone library. "
+            "Update Python to version 3.9 or newer, or install pytz."
+        )