port matrix-ops-bot to uv and nix flake module

ops_bot/util/template.py

@@ -13,6 +13,7 @@
 #
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
+import os
 import os.path
 from pathlib import Path
 from typing import Any, Callable, Dict, List, Tuple, Union
@@ -113,7 +114,11 @@ class PluginTemplateLoader(BaseLoader):
     macros: str
 
     def __init__(self, base: str, directory: str) -> None:
-        base_path = get_project_root() / ".." / "templates" / base
+        template_root = os.environ.get("OPS_BOT_TEMPLATE_ROOT")
+        if template_root is None:
+            template_root = str(get_project_root() / ".." / "templates")
+        template_root_path = Path(template_root)
+        base_path = template_root_path / base
         self.directory = base_path / directory
         self.macros = sync_read_file(base_path / "macros.html")