bump the minimum supported Python version to 3.8

The previous commit started using `shutil.copytree` in the `cp` plugin,
which requires Python 3.8. That plugin isn't often used outside of
testing, so 3.5-3.7 are likely to keep working for a while, but 3.7 has
been EOL since 2023 anyway.

.github/workflows/push.yml

@@ -13,15 +13,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.5", "3.6", "3.7", "3.8", "3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
         os: [ubuntu-latest, windows-latest, macOS-latest]
-        exclude:
-          # No longer supported on GitHub CI.
-          - python-version: 3.5
-            os: "ubuntu-latest"
-          - python-version: 3.6
-            os: "ubuntu-latest"
-
 
     steps:
     - uses: actions/checkout@v4

README.md

@@ -35,7 +35,7 @@ It also happens to be an anagram for "[reup](#magical-updates)".
 
 Peru supports Linux, macOS, and Windows. It requires:
 
-* `python` 3.5 or later
+* `python` 3.8 or later
 * `git`, any version
 * optionally, if you want fetch from these types of repos:
   * `hg`, any version
@@ -54,10 +54,6 @@ pip install peru
 
 Note that depending on how Python is set up on your machine, you might
 need to use `sudo` with that, and Python 3's pip might be called `pip3`.
-Also, if you have to use Python 3.3 or 3.4, those were supported up to
-peru 1.1.4.
-
-Don't forget to install `git`, too, however is appropriate for your OS.
 
 ### Using OS package managers