Fix CI test issue whereby nvim-treesitter changed their whole deal

https://github.com/nvim-treesitter/nvim-treesitter indicates they did
a full rewrite which is incompatible. Currently, their latest is giving
all kinds of verification issues downloading tarballs. Maybe some day
in the future we should switch back from master to main (they say
    master will hang around for compat)

Author: aaronik

Makefile

@@ -17,13 +17,13 @@ test-watch: ## uses [nodemon](https://nodemon.io/) - watches for changes to lua
 test-ubuntu: ## Run tests in Ubuntu Docker container (matches CI environment)
 	@docker run --rm -v $$(PWD):/workspace -w /workspace ubuntu:latest bash -c "\
 		apt-get update && \
-		apt-get install -y software-properties-common git curl make apt-utils gcc && \
+		apt-get install -y software-properties-common git curl make apt-utils gcc g++ && \
 		add-apt-repository -y ppa:neovim-ppa/unstable && \
 		apt-get update && \
 		apt-get install -y neovim lua-check && \
 		mkdir -p /root/.local/share/nvim/lazy/ && \
 		git clone --depth 1 https://github.com/nvim-lua/plenary.nvim.git /root/.local/share/nvim/lazy/plenary.nvim && \
-		git clone --depth 1 https://github.com/nvim-treesitter/nvim-treesitter.git /root/.local/share/nvim/lazy/nvim-treesitter && \
+		git clone --depth 1 --branch master https://github.com/nvim-treesitter/nvim-treesitter.git /root/.local/share/nvim/lazy/nvim-treesitter && \
 		make test"
 
 check: ## uses [luacheck](https://github.com/mpeterv/luacheck) - checks for any type errors or style issues

tests/minimal_init.lua

@@ -9,7 +9,15 @@ vim.opt.swapfile = false
 vim.cmd("runtime! plugin/treewalker.nvim")
 vim.cmd("runtime! plugin/plenary.vim")
 vim.cmd("runtime! plugin/nvim-treesitter")
-require('nvim-treesitter.configs').setup {
+
+-- nvim-treesitter renamed `nvim-treesitter.configs` -> `nvim-treesitter.config`.
+-- Keep tests working across versions.
+local ok, ts_config = pcall(require, "nvim-treesitter.configs")
+if not ok then
+  ts_config = require("nvim-treesitter.config")
+end
+
+ts_config.setup {
     ensure_installed = {
         "lua",
         "c",
@@ -42,5 +50,6 @@ vim.treesitter.language.register('javascript', { 'js' })
 vim.treesitter.language.register('scheme', { 'scm' })
 vim.treesitter.language.register('yaml', { 'yml' })
 vim.treesitter.language.register('go', { 'go' })
+vim.treesitter.language.register('python', { 'py' })
 
 dofile("plugin/init.lua") -- get the Treewalker command present