Support building on M1 macs

[deeplow]

The shiboken2 package fails to install on m1s because it has no builds for ARM architectures on macbooks (no available wheels).

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When running poetry install on an m1 macbook:

Originally posted by @deeplow in #172 (comment)

[deeplow]

Confirmed by @gmarmstrong in #161 (comment).

[deeplow]

To clarify, Dangerzone runs fine on m1 macs. What I can't seem to do is to setup the development environment due to dependency issues (shiboken).

[deeplow]

Until this this addressed, installing on M1 macs will involve activating rosetta (Apple's amd64 to arm emulation layer)

I had not seen this before when setting up on an m1 mac but that was probably due to the machine being already provisioned with rosetta.

[deeplow]

Our current approach to may be :

try: 
  Pyside2...
except ImportError:
  PySide6...

or maybe we should do with platform conditions.

On Poetry - find a way to have platform-specific dependencies - Add PySide6 for MacOS.

[apyrgio]

Update regarding the final implementation of this feature:

1. PySide6 does not have sufficient type checking stubs, so we can't use Mypy to check it (see PySide6 does not offer sufficient Mypy hints #320). To circumvent this issue, we always perform type checking with the PySide2 stubs, since the API is compatible.

   • A problem with the existing PySide2 stubs is that they also bring PySide2 as a dependency. This means that in dev environments where we install PySide6 (currently Windows and MacOS), we would need to install PySide2 as well, which would potentially mask import problems. Worse, for MacOS M1 machines, this is not possible to do in the first place, since we can't install PySide2.

     A solution to this problem is to replace PySide2-stubs with types-PySide2, which does not have this dependency, and has better Mypy stubs.

2. From now on, we will prefer PySide6 instead of PySide2, in systems that offer it. This means that we will try first importing PySide6, and then fallback to PySide2.

3. The QRegExp class does not exist in PySide6. In their docs, they propose using QRegularExpression in Qt5, as a migration path towards Qt6. From a cursory glance on the sole regular expression that we use, we should not be affected by this change, so we will use this class.