Fail gracefully if config lacks the mandatory main section

Currently, if a user didn't put `[general]` section in config file,
bugwarrior fails like this:

    Traceback (most recent call last):
      File "/usr/bin/bugwarrior", line 8, in <module>
        sys.exit(cli())
                 ~~~^^
      File "/usr/lib/python3.14/site-packages/click/core.py", line 1485, in __call__
        return self.main(*args, **kwargs)
               ~~~~~~~~~^^^^^^^^^^^^^^^^^
      File "/usr/lib/python3.14/site-packages/click/core.py", line 1406, in main
        rv = self.invoke(ctx)
      File "/usr/lib/python3.14/site-packages/click/core.py", line 1873, in invoke
        return _process_result(sub_ctx.command.invoke(sub_ctx))
                               ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
      File "/usr/lib/python3.14/site-packages/click/core.py", line 1269, in invoke
        return ctx.invoke(self.callback, **ctx.params)
               ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/usr/lib/python3.14/site-packages/click/core.py", line 824, in invoke
        return callback(*args, **kwargs)
      File "/usr/lib/python3.14/site-packages/click/decorators.py", line 34, in new_func
        return f(get_current_context(), *args, **kwargs)
      File "/usr/lib/python3.14/site-packages/bugwarrior/command.py", line 62, in wrapped_subcommand_callback
        return ctx.invoke(subcommand_callback, *args, **kwargs)
               ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/usr/lib/python3.14/site-packages/click/core.py", line 824, in invoke
        return callback(*args, **kwargs)
      File "/usr/lib/python3.14/site-packages/bugwarrior/command.py", line 105, in pull
        config = _try_load_config(main_section, interactive, quiet)
      File "/usr/lib/python3.14/site-packages/bugwarrior/command.py", line 35, in _try_load_config
        return load_config(main_section, interactive, quiet)
      File "/usr/lib/python3.14/site-packages/bugwarrior/config/load.py", line 122, in load_config
        rawconfig['flavor'][main_section]['interactive'] = interactive
        ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
    KeyError: 'general'

This is confusing — it looks more like bugwarrior broke due to some
API change in Python, rather than because of a user mistake.

So handle this case with explicit check. Now it will fail instead like
this:

    CRITICAL:bugwarrior.command:Could not load configuration. Maybe you have not created a configuration file.
    bugwarrior.config.load.ErrConfigLacksSection: Configuration lacks section "general"

Author: Hi-Angel

bugwarrior/command.py

@@ -10,7 +10,7 @@
 from lockfile.pidlockfile import PIDLockFile
 
 from bugwarrior.collect import aggregate_issues, get_service
-from bugwarrior.config import get_config_path, get_keyring, load_config
+from bugwarrior.config import get_config_path, get_keyring, load_config, ErrConfigLacksSection
 from bugwarrior.db import get_defined_udas_as_strings, synchronize
 
 if TYPE_CHECKING:
@@ -33,7 +33,7 @@ def _try_load_config(
 ) -> "Config":
     try:
         return load_config(main_section, interactive, quiet)
-    except OSError:
+    except (OSError, ErrConfigLacksSection):
         # Our standard logging configuration depends on the bugwarrior
         # configuration file which just failed to load.
         logging.basicConfig()

bugwarrior/config/load.py

@@ -115,10 +115,14 @@ def parse_file(configpath: str) -> dict:
         config = parse_ini_file(configpath)
     return format_config(config)
 
+class ErrConfigLacksSection(Exception):
+    """Raised if config lacks a section"""
 
 def load_config(main_section, interactive, quiet) -> Config:
     configpath = get_config_path()
     rawconfig = parse_file(configpath)
+    if main_section not in rawconfig['flavor']:
+        raise ErrConfigLacksSection(f'Configuration lacks section "{main_section}"')
     rawconfig['flavor'][main_section]['interactive'] = interactive
     config = validate_config(rawconfig, main_section, configpath)
     configure_logging(