Make tests work reliably on the Pi

While the tests work well on a PC or Travis, the Pi (where I ought to be
running them!) has some issues with the timing tests. Need to relax the
tolerance of the "assert_states_and_times" method to 0.05 seconds
otherwise it periodically fails even on something reasonably quick like
a Pi 2 (less failures on a Pi 3 but still occasionally).

Also reduced default fps to 25; if the default timing occasionally fails
on a Pi 2 it's evidently too fast for a Pi 1 and shouldn't be the
default; 25 also doesn't look any different to me on a pulsing LED.

There's also a bunch of miscellaneous fixes in here; last minute typos
and chart re-gens for the 1.2 release.

gpiozero/__init__.py

@@ -121,19 +121,3 @@ from .other_devices import (
     PingServer,
     TimeOfDay,
 )
-from .source_tools import (
-    averaged,
-    clamped,
-    conjunction,
-    cos_values,
-    disjunction,
-    inverted,
-    negated,
-    post_delayed,
-    pre_delayed,
-    quantized,
-    queued,
-    random_values,
-    scaled,
-    sin_values,
-)

gpiozero/boards.py

@@ -258,7 +258,7 @@ class LEDBoard(LEDCollection):
             on_time, off_time, fade_in_time, fade_out_time, n, background
         )
 
-    def _blink_device(self, on_time, off_time, fade_in_time, fade_out_time, n, fps=50):
+    def _blink_device(self, on_time, off_time, fade_in_time, fade_out_time, n, fps=25):
         sequence = []
         if fade_in_time > 0:
             sequence += [

gpiozero/devices.py

@@ -107,7 +107,13 @@ class GPIOMeta(type):
                         try:
                             old_close()
                         finally:
-                            del cls._INSTANCES[key]
+                            try:
+                                del cls._INSTANCES[key]
+                            except KeyError:
+                                # If the _refs go negative (too many closes)
+                                # just ignore the resulting KeyError here -
+                                # it's already gone
+                                pass
                 self.close = close
                 cls._INSTANCES[key] = weakref.proxy(self)
         else:

gpiozero/mixins.py

@@ -374,7 +374,7 @@ class HoldMixin(EventsMixin):
     @hold_time.setter
     def hold_time(self, value):
         if value < 0:
-            raise BadWaitTime('source_delay must be 0 or greater')
+            raise BadWaitTime('hold_time must be 0 or greater')
         self._hold_time = float(value)
 
     @property
@@ -403,8 +403,8 @@ class HoldMixin(EventsMixin):
         The length of time (in seconds) that the device has been held for.
         This is counted from the first execution of the :attr:`when_held` event
         rather than when the device activated, in contrast to
-        :attr:`active_time`. If the device is not currently held, this is
-        ``None``.
+        :attr:`~EventsMixin.active_time`. If the device is not currently held,
+        this is ``None``.
         """
         if self._held_from is not None:
             return time() - self._held_from

gpiozero/output_devices.py

@@ -19,8 +19,8 @@ class OutputDevice(SourceMixin, GPIODevice):
     Represents a generic GPIO output device.
 
     This class extends :class:`GPIODevice` to add facilities common to GPIO
-    output devices: an :meth:`on` method to switch the device on, and a
-    corresponding :meth:`off` method.
+    output devices: an :meth:`on` method to switch the device on, a
+    corresponding :meth:`off` method, and a :meth:`toggle` method.
 
     :param int pin:
         The GPIO pin (in BCM numbering) that the device is connected to. If
@@ -123,10 +123,9 @@ class DigitalOutputDevice(OutputDevice):
     """
     Represents a generic output device with typical on/off behaviour.
 
-    This class extends :class:`OutputDevice` with a :meth:`toggle` method to
-    switch the device between its on and off states, and a :meth:`blink` method
-    which uses an optional background thread to handle toggling the device
-    state without further interaction.
+    This class extends :class:`OutputDevice` with a :meth:`blink` method which
+    uses an optional background thread to handle toggling the device state
+    without further interaction.
     """
     def __init__(self, pin=None, active_high=True, initial_value=False):
         self._blink_thread = None
@@ -458,7 +457,7 @@ class PWMOutputDevice(OutputDevice):
             self._blink_thread = None
 
     def _blink_device(
-            self, on_time, off_time, fade_in_time, fade_out_time, n, fps=50):
+            self, on_time, off_time, fade_in_time, fade_out_time, n, fps=25):
         sequence = []
         if fade_in_time > 0:
             sequence += [
@@ -686,7 +685,7 @@ class RGBLED(SourceMixin, Device):
 
     def _blink_device(
             self, on_time, off_time, fade_in_time, fade_out_time, on_color,
-            off_color, n, fps=50):
+            off_color, n, fps=25):
         # Define some simple lambdas to perform linear interpolation between
         # off_color and on_color
         lerp = lambda t, fade_in: tuple(

gpiozero/pins/mock.py

@@ -159,7 +159,7 @@ class MockPin(Pin):
         # that's about all we can reasonably expect in a non-realtime
         # environment on a Pi 1)
         for actual, expected in zip(self.states, expected_states):
-            assert isclose(actual.timestamp, expected[0], rel_tol=0.01, abs_tol=0.01)
+            assert isclose(actual.timestamp, expected[0], rel_tol=0.05, abs_tol=0.05)
             assert isclose(actual.state, expected[1])