Emit internet-available.target from the dhcp hook

Logging: Prevent tracebacks when argv is not accessible

The logger attempts to read `sys.argv` to determine the executable name
which is doing the logging. There are some ways of launching the logger
(e.g. when using it through one of the C++ Python wrappers) which cause
it to not have this property so the functions traceback. Resolve this by
providing a default value in the event that this isn't set.

Flake8 fix ignore docs

Fixed an issue with is_internet failing due to network iface name change

In Stretch, the ifaces now use predictable naming conventions and
have moved away from wlan0 or eth0. If the kernel option net.ifnames=0
is missing from a Stretch image, these hardcoded iface name tests might
fail.

It was observed that on an upgraded 3.14.0 image that the script
failed when using ethernet and the kernel option was not present since
eth iface was renamed but the wlan one was not. As such, connecting
to WiFi made the script succeed.

Fixed an issue with is_internet failing due to network iface name change

In Stretch, the ifaces now use predictable naming conventions and
have moved away from wlan0 or eth0. If the kernel option net.ifnames=0
is missing from a Stretch image, these hardcoded iface name tests might
fail.

It was observed that on an upgraded 3.14.0 image that the script
failed when using ethernet and the kernel option was not present since
eth iface was renamed but the wlan one was not. As such, connecting
to WiFi made the script succeed.

Logging: Fix logging tracebacks

When a program traces back, the logger will attempt to log it. However,
it is stored as a JSON in an intermediate form. This causes the
`json.dumps()` method to be invoked which, unfortunately, doesn't know
how to encode `Exception`s and thus traces back itself causing the
original traceback to be lost. Resolve this problem by casting
beforehand.

Logging: Fix logging tracebacks

When a program traces back, the logger will attempt to log it. However,
it is stored as a JSON in an intermediate form. This causes the
`json.dumps()` method to be invoked which, unfortunately, doesn't know
how to encode `Exception`s and thus traces back itself causing the
original traceback to be lost. Resolve this problem by casting
beforehand.

Bug/wifi hooks (#286)

* Defining currently undescribed triggers for network hooks.

* Added dhcpcd changes.

* Typos, Trigger Hooks, Identing

- Corrected typos and code indentation
- Added a new trigger signal
- Included comment about already described connected behaviour

Bug/wifi hooks (#286)

* Defining currently undescribed triggers for network hooks.

* Added dhcpcd changes.

* Typos, Trigger Hooks, Identing

- Corrected typos and code indentation
- Added a new trigger signal
- Included comment about already described connected behaviour

Bug/wifi hooks (#286)

* Defining currently undescribed triggers for network hooks.

* Added dhcpcd changes.

* Typos, Trigger Hooks, Identing

- Corrected typos and code indentation
- Added a new trigger signal
- Included comment about already described connected behaviour