Pyvisa-py

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- fix writing large messages over TCPIP using the VXI-11 protocol PR 343
- add support for the hislip protocol over TCPIP PR 331
- allow to list TCPIP resources PR 326
In order to discover resources over all subnets psutil needs to be installed
- attempt to stabilize access to USBTMC resources PR 335
Reduce the number of device reset performed and only set all settings if it
is meaningful (more than one settings exist.)

A huge thanks to bobmacnamara for his work adding hislip and vicp support !

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- fix tcp/ip connections dropping from inside Docker containers after 5 minute idling 285
- fix ControlFlow.none as an invalid attribute in serial.py PR 317
- VXI11 bug fix: skip over stale rx packets instead of raising an exception. PR 322
- VXI11 bug fix: to ensure all data gets sent, replace calls to sock.send()
with calls to sock.sendall(), and replace calls to sock.sendto() with
calls to a routine that loops until all data is sent. PR 322

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- handle SUPPRESS_END_EN in usb.py to fix 293 PR 294
- add python_requires to avoid people trying to get a
new pyvisa-py on Python 2 PR 295
This addresses pyvisa issue 578

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- list serial resources under Windows without the COM prefix 269
- fix writing to serial resources PR 277
- fix return value of USB close method PR 265
- fix pyvisa version constraint PR 268

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In 0.5.0, the Python package installed in site-packages in now called pyvisa_py
which makes it a valid python package. This change was decided because the old name
was causing issues with tools such as Mypy and PyInstaller.

- start running testsuite on Keysight buildbot PR 247 252
- fix import in gpib.py when using linux-gpib PR 246
- fix opening some TCPIP resources PR 242
Some instrument do not indicate that the returned packet is the last one, so
fix the number of returned packet for a TCPIP INSTR resource.
- add typing validation through mypy PR 238
- use Numpy style dosctrings PR 238
- format the code with black and isort PR 236
- drop Python 2 support and run against PyVISA 1.11 PR 222
- usbtmc: improve support for USB488 devices. PR 241
For instrument that support REN_CONTROL, we now always assert the REN line.
- fix a crash on Windows when opening multiple USBTMC devices

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- fix typo in tcpip.py PR 233 (back-ported)