dist/tools/pyterm: set exclusive access on port

[benpicco]

Contribution description

A common source of error is that a user connects to a serial port that has already been opened in another terminal.
This may lead to garbled output or no output at all.

To avoid this, claim exclusive access on the serial port so we get a proper error instead of corrupted output.

Testing procedure

Connect to a serial port

$ ./dist/tools/pyterm/pyterm
2023-09-13 12:07:44,770 # Connect to serial port /dev/ttyUSB0
Welcome to pyterm!
Type '/exit' to exit.

Now try to open the same port again in a different terminal

$ ./dist/tools/pyterm/pyterm
2023-09-13 12:08:07,907 # Connect to serial port /dev/ttyUSB0
2023-09-13 12:08:07,908 # Could not exclusively lock port /dev/ttyUSB0: [Errno 11] Resource temporarily unavailable
2023-09-13 12:08:07,908 # Trying to reconnect to /dev/ttyUSB0 in 10 sec
2023-09-13 12:08:17,909 # Could not exclusively lock port /dev/ttyUSB0: [Errno 11] Resource temporarily unavailable

Issues/PRs references

[riot-ci]

Murdock results

✔️ PASSED

dad593a dist/tools/pyterm: set exclusive access on port

Success	Failures	Total	Runtime
1	0	1	01m:20s

Artifacts

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[benpicco]

bors merge

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