Remove Python 3.7 support.

Make corresponding changes to other files (including a few that I
missed before).

.github/workflows/python-package.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11"]
+        python-version: ["3.8", "3.9", "3.10", "3.11"]
 
     steps:
     - uses: actions/checkout@v2

README.md

@@ -24,7 +24,7 @@ The code in this repository is named _PROPKA 3_ and it is based on the original
 
 ## Requirements
 
-PROPKA 3 requires Python 3.6 or higher.  Additional requirements are specified in the `requirements.txt` file and automatically satisfied when installing with [pip](https://pip.pypa.io).
+PROPKA 3 requires Python 3.8 or higher.  Additional requirements are specified in the `requirements.txt` file and automatically satisfied when installing with [pip](https://pip.pypa.io).
 
 ## Installation
 

docs/source/changelog.rst

@@ -8,7 +8,7 @@ Current version
 Changes
 -------
 
-* Remove support for Python 3.6; add support for up to Python 3.11.
+* Remove support for Python 3.6 and 3.7; add support for up to Python 3.11.
 
 v3.4.0
 ======

docs/source/installation.rst

@@ -5,7 +5,7 @@
 ==============
 
 
-PROPKA 3 requires Python 3.6 or higher. Additional requirements are
+PROPKA 3 requires Python 3.8 or higher. Additional requirements are
 specified in the :file:`requirements.txt` file and automatically satisfied
 when installing with pip_.
 

setup.py

@@ -59,7 +59,7 @@ See http://propka.org/ for the PROPKA web server.
     package_data={'propka': ['*.dat', '*.cfg', '*.json']},
     entry_points={'console_scripts': ['propka3 = propka.run:main', ]},
     zip_safe=True,
-    python_requires='>=3.6',
+    python_requires='>=3.8',
     tests_require=["numpy", "pytest"],
     test_suite="tests",
     )