Implemented log.exception, improved logging

Removed unused code

src/trezor/layout.py

@@ -2,7 +2,7 @@ import sys
 import utime
 from . import utils
 
-import log
+from . import log
 
 _new_layout = None
 _current_layout = None

src/trezor/log.py

@@ -1,3 +1,4 @@
+import _io
 import sys
 import utime
 
@@ -39,5 +40,10 @@ def warning(name, msg, *args):
 def error(name, msg, *args):
     _log(name, ERROR, msg, *args)
 
+def exception(name, exc):
+    out = _io.StringIO()
+    sys.print_exception(exc, out)
+    _log(name, ERROR, out.getvalue())
+
 def critical(name, msg, *args):
     _log(name, CRITICAL, msg, *args)

src/trezor/loop.py

@@ -1,5 +1,4 @@
 import utime
-import sys
 
 from uheapq import heappop, heappush
 from .utils import type_gen
@@ -12,8 +11,6 @@ EVT_TMOVE = const(-2)
 EVT_TEND = const(-3)
 EVT_MSG = const(-4)
 
-DO_NOTHING = const(-5)
-
 evt_handlers = { EVT_TSTART: None,
                  EVT_TMOVE: None,
                  EVT_TEND: None,
@@ -114,18 +111,13 @@ def run_forever(start_gens):
             # gen ended, forget it and go on
             continue
         except Exception as e:
-            # FIXME
-            log.error(__name__, str(e))
-            sys.print_exception(e)
-            # log.exception(__name__, e)
+            log.exception(__name__, e)
             continue
 
         if isinstance(ret, int):
             if ret >= 0:
                 # sleep until ret, call us later
                 __call_at(ret, gen)
-            elif ret == DO_NOTHING:
-                print("Removing gen from time queue")
             else:
                 # wait for event
                 raise NotImplementedError()