[core] Allow module loading from user directory

If a module fails to load from both core and contrib, fall back to
loading by file name from "~/.config/bumblebee-status/modules/<name>.py"

fixes #757

bumblebee_status/core/module.py

@@ -17,6 +17,7 @@ except Exception as e:
 
 log = logging.getLogger(__name__)
 
+import sys
 
 """Loads a module by name
 
@@ -45,7 +46,14 @@ def load(module_name, config=core.config.Config([]), theme=None):
             log.debug("importing {} from contrib".format(module_short))
             return getattr(mod, "Module")(config, theme)
         except ImportError as e:
-            log.fatal("failed to import {} from contrib: {}".format(module_short, e))
+            try:
+                log.warning("failed to import {} from system: {}".format(module_short, e))
+                mod = importlib.machinery.SourceFileLoader("modules.{}".format(module_short),
+                    os.path.expanduser("~/.config/bumblebee-status/modules/{}.py".format(module_short))).load_module()
+                log.debug("importing {} from user".format(module_short))
+                return getattr(mod, "Module")(config, theme)
+            except ImportError as e:
+                log.fatal("failed to import {}: {}".format(module_short, e))
     return Error(config=config, module=module_name, error="unable to load module")
 
 

docs/development/module.rst

@@ -11,6 +11,7 @@ Adding a new module to ``bumblebee-status`` is straight-forward:
    ``bumblebee-status`` (i.e. a module called
    ``bumblebee_status/modules/contrib/test.py`` will be loaded using
    ``bumblebee-status -m test``)
+-  Alternatively, you can put your module in ``~/.config/bumblebee-status/modules/``
 -  The module name must follow the `Python Naming Conventions <https://www.python.org/dev/peps/pep-0008/#package-and-module-names>`_
 -  See below for how to actually write the module
 -  Test (run ``bumblebee-status`` in the CLI)