general: add compat module and helper for easy backwards compatibiltity for pre-PIP dependencies

my.hypothesis: use hypexport as a proper PIP package + fallback

my/core/compat.py

@@ -0,0 +1,49 @@
+'''
+Some backwards compatibility stuff/deprecation helpers
+'''
+import warnings
+
+from ..common import LazyLogger
+
+
+logger = LazyLogger('my.core.compat')
+
+
+def pre_pip_dal_handler(
+        name: str,
+        e: ModuleNotFoundError,
+        cfg,
+        requires=[],
+) -> None:
+    '''
+    https://github.com/karlicoss/HPI/issues/79
+    '''
+    if e.name != name:
+        # the module itself was imported, so the problem is with some dependencies
+        raise e
+    try:
+        dal = _get_dal(cfg, name)
+        # todo this is fairly high severity, would be nice to highlight in the terminal or something
+        warnings.warn(f'''
+Specifying modules' dependencies in the config or in my/config/repos is deprecated!
+Please install {' '.join(requires)} as PIP packages (see the corresponding README instructions).
+'''.strip())
+    except ModuleNotFoundError as ee:
+        dal = None
+
+    if dal is None:
+        # probably means there was nothing in the old config in the first place
+        # so we should raise the original exception
+        raise e
+    return dal
+
+
+def _get_dal(cfg, module_name: str):
+    mpath = getattr(cfg, module_name, None)
+    if mpath is not None:
+        from .common import import_dir
+        return import_dir(mpath, '.dal')
+    else:
+        from importlib import import_module
+        return import_module(f'my.config.repos.{module_name}.dal')
+