dev env: add missing backports.zoneinfo package

Pipfile

@@ -20,6 +20,19 @@ pytest-cov = "*"
 # > ModuleNotFoundError: No module named 'typing_extensions'
 typing_extensions = {version = "*", markers = ""}
 
+# python<=3.8 compatibility
+# > [...]/python3.8/site-packages/telegram/ext/jobqueue.py:27: in <module>
+# >     from apscheduler.schedulers.background import BackgroundScheduler
+# > [...]
+# > [...]/python3.8/site-packages/tzlocal/unix.py:6: in <module>
+# >     import pytz_deprecation_shim as pds
+# > [...]
+# > [...]/python3.8/site-packages/pytz_deprecation_shim/_compat_py3.py:7: in <module>
+# >     from backports import zoneinfo
+# > E   ModuleNotFoundError: No module named 'backports'
+# > Error: Process completed with exit code 4.
+"backports.zoneinfo" = {version = "*", markers = "python_version <= '3.8'"}
+
 [requires]
 python_version = "3"
 

Pipfile.lock

@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "c78cf9b450b7106e77d0041ee6a15576163ceadad8ff5edabc234980b7e25896"
+            "sha256": "ba5255eb9a59e8c118113f63feaea26057d07465d2030b01ba3ce2a1815a4e87"
         },
         "pipfile-spec": 6,
         "requires": {
@@ -165,6 +165,29 @@
             "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4'",
             "version": "==21.2.0"
         },
+        "backports.zoneinfo": {
+            "hashes": [
+                "sha256:17746bd546106fa389c51dbea67c8b7c8f0d14b5526a579ca6ccf5ed72c526cf",
+                "sha256:1b13e654a55cd45672cb54ed12148cd33628f672548f373963b0bff67b217328",
+                "sha256:1c5742112073a563c81f786e77514969acb58649bcdf6cdf0b4ed31a348d4546",
+                "sha256:4a0f800587060bf8880f954dbef70de6c11bbe59c673c3d818921f042f9954a6",
+                "sha256:5c144945a7752ca544b4b78c8c41544cdfaf9786f25fe5ffb10e838e19a27570",
+                "sha256:7b0a64cda4145548fed9efc10322770f929b944ce5cee6c0dfe0c87bf4c0c8c9",
+                "sha256:8439c030a11780786a2002261569bdf362264f605dfa4d65090b64b05c9f79a7",
+                "sha256:8961c0f32cd0336fb8e8ead11a1f8cd99ec07145ec2931122faaac1c8f7fd987",
+                "sha256:89a48c0d158a3cc3f654da4c2de1ceba85263fafb861b98b59040a5086259722",
+                "sha256:a76b38c52400b762e48131494ba26be363491ac4f9a04c1b7e92483d169f6582",
+                "sha256:da6013fd84a690242c310d77ddb8441a559e9cb3d3d59ebac9aca1a57b2e18bc",
+                "sha256:e55b384612d93be96506932a786bbcde5a2db7a9e6a4bb4bffe8b733f5b9036b",
+                "sha256:e81b76cace8eda1fca50e345242ba977f9be6ae3945af8d46326d776b4cf78d1",
+                "sha256:e8236383a20872c0cdf5a62b554b27538db7fa1bbec52429d8d106effbaeca08",
+                "sha256:f04e857b59d9d1ccc39ce2da1021d196e47234873820cbeaad210724b1ee28ac",
+                "sha256:fadbfe37f74051d024037f223b8e001611eac868b5c5b06144ef4d8b799862f2"
+            ],
+            "index": "pypi",
+            "markers": "python_version <= '3.8'",
+            "version": "==0.2.1"
+        },
         "black": {
             "hashes": [
                 "sha256:1c02557aa099101b9d21496f8a914e9ed2222ef70336404eeeac8edba836fbea"