[core] Refactor engine

This is going to be a bit more comprehensive than anticipated. In order
to cleanly refactor the core and the engine, basically start from
scratch with the implementation.

Goals:

* Test coverage
* Maintain backwards compatibility with module interface as much as
  possible (but still make modules easier to code)
* Simplicity

see #23

bumblebee/modules/dnf.py

@@ -1,98 +0,0 @@
-from __future__ import absolute_import
-
-import time
-import shlex
-import threading
-import subprocess
-
-import bumblebee.module
-import bumblebee.util
-
-def description():
-    return "Checks DNF for updated packages and displays the number of <security>/<bugfixes>/<enhancements>/<other> pending updates."
-
-def parameters():
-    return [ "dnf.interval: Time in seconds between two checks for updates (defaults to 1800)" ]
-
-def get_dnf_info(obj):
-    loops = obj.interval()
-
-    for thread in threading.enumerate():
-        if thread.name == "MainThread":
-            main = thread
-
-    while main.is_alive():
-        loops += 1
-        if loops < obj.interval():
-            time.sleep(1)
-            continue
-
-        loops = 0
-        try:
-            res = subprocess.check_output(shlex.split("dnf updateinfo"))
-        except Exception as e:
-            break
-
-        security = 0
-        bugfixes = 0
-        enhancements = 0
-        other = 0
-        for line in res.decode().split("\n"):
-
-            if not line.startswith(" "): continue
-            elif "ecurity" in line:
-                for s in line.split():
-                    if s.isdigit(): security += int(s)
-            elif "ugfix" in line:
-                for s in line.split():
-                    if s.isdigit(): bugfixes += int(s)
-            elif "hancement" in line:
-                for s in line.split():
-                    if s.isdigit(): enhancements += int(s)
-            else:
-                for s in line.split():
-                    if s.isdigit(): other += int(s)
-
-        obj.set("security", security)
-        obj.set("bugfixes", bugfixes)
-        obj.set("enhancements", enhancements)
-        obj.set("other", other)
-
-class Module(bumblebee.module.Module):
-    def __init__(self, output, config):
-        super(Module, self).__init__(output, config)
-
-        self._counter = {}
-        self._thread = threading.Thread(target=get_dnf_info, args=(self,))
-        self._thread.start()
-
-    def interval(self):
-        return self._config.parameter("interval", 30*60)
-
-    def set(self, what, value):
-        self._counter[what] = value
-
-    def get(self, what):
-        return self._counter.get(what, 0)
-
-    def widgets(self):
-        result = []
-        for t in [ "security", "bugfixes", "enhancements", "other" ]:
-            result.append(str(self.get(t)))
-
-        return bumblebee.output.Widget(self, "/".join(result))
-
-    def state(self, widget):
-        total = sum(self._counter.values())
-        if total == 0: return "good"
-        return "default"
-
-    def warning(self, widget):
-        total = sum(self._counter.values())
-        return total > 0
-
-    def critical(self, widget):
-        total = sum(self._counter.values())
-        return total > 50 or self._counter.get("security", 0) > 0
-
-# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4