Make sure Astral 2 or higher is installed

Also enforce Python 3.6 which is required by Astral 2

Makefile

@@ -7,5 +7,6 @@ README.rst: README.md
 	pandoc --from markdown --to rst --output=README.rst README.md
 
 dist: README.rst
+	rm -fr dist
 	python3 setup.py sdist bdist_wheel
 

README.md

@@ -8,7 +8,7 @@ gw2pvo is a command line tool to upload solar data from a GoodWe power inverter
 You need to have Python 3 and pip installed. Then:
 
 ```shell
-sudo pip3 install https://github.com/markruys/gw2pvo/releases/download/1.3.2/gw2pvo-1.3.2-py3-none-any.whl
+sudo pip3 install https://github.com/markruys/gw2pvo/releases/download/1.3.3/gw2pvo-1.3.3-py3-none-any.whl
 ```
 
 Next determine the Station ID from the GoodWe site as follows. Open the [Sems Portal](https://www.semsportal.com). The Plant Status will reveal the Station ID in the URL. Example:

gw2pvo/__init__.py

@@ -1,3 +1,3 @@
-__version__ = "1.3.2"
+__version__ = "1.3.3"
 
 __all__ = [ 'gw_api', 'gw_csv', 'pvo_api' ]

gw2pvo/__main__.py

@@ -1,14 +1,19 @@
 #!/usr/bin/env python3
 
 import sys
+if sys.version_info < (3,6):
+    sys.exit('Sorry, you need at least Python 3.6 for Astral 2')
+
 import logging
 import argparse
 import locale
 import time
 from datetime import datetime
+
 from astral import LocationInfo
 from astral.geocoder import lookup, database
 from astral.location import Location
+
 from gw2pvo import ds_api
 from gw2pvo import gw_api
 from gw2pvo import gw_csv
@@ -106,8 +111,8 @@ def run():
     parser.add_argument("--gw-station-id", help="GoodWe station ID", metavar='ID', required=True)
     parser.add_argument("--gw-account", help="GoodWe account", metavar='ACCOUNT', required=True)
     parser.add_argument("--gw-password", help="GoodWe password", metavar='PASSWORD', required=True)
-    parser.add_argument("--pvo-system-id", help="PVOutput system ID", metavar='ID', required=not True)
-    parser.add_argument("--pvo-api-key", help="PVOutput API key", metavar='KEY', required=not True)
+    parser.add_argument("--pvo-system-id", help="PVOutput system ID", metavar='ID')
+    parser.add_argument("--pvo-api-key", help="PVOutput API key", metavar='KEY')
     parser.add_argument("--pvo-interval", help="PVOutput interval in minutes", type=int, choices=[5, 10, 15])
     parser.add_argument("--darksky-api-key", help="Dark Sky Weather API key")
     parser.add_argument("--log", help="Set log level (default info)", choices=['debug', 'info', 'warning', 'critical'], default="info")

setup.py

@@ -5,10 +5,6 @@
 https://github.com/markruys/gw2pvo
 """
 
-import sys
-if sys.version_info < (3,3):
-    sys.exit('Sorry, you need at least Python 3.3.0')
-
 # Always prefer setuptools over distutils
 from setuptools import setup, find_packages
 # To use a consistent encoding
@@ -59,9 +55,9 @@
         'License :: OSI Approved :: MIT License',
 
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.3',
-        'Programming Language :: Python :: 3.4',
-        'Programming Language :: Python :: 3.5',
+        'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
+        'Programming Language :: Python :: 3.8',
     ],
 
     # What does your project relate to?
@@ -79,7 +75,10 @@
     # your project is installed. For an analysis of "install_requires" vs pip's
     # requirements files see:
     # https://packaging.python.org/en/latest/requirements.html
-    install_requires=['astral', 'requests'],
+    install_requires=['astral>=2', 'requests'],
+
+    # Astral >=2 requires Python>=3.6
+    python_requires='>=3.6',
 
     # List additional groups of dependencies here (e.g. development
     # dependencies). You can install these using the following syntax,