docs: warn against bleak.py

We frequently get bug reports about circular import errors. This is
due to naming your script bleak.py. So put warnings everywhere so
hopefully people won't miss it.

Fixes: hbldh#729
Fixes: hbldh#704
Fixes: hbldh#515

README.rst

@@ -84,6 +84,7 @@ Connect to a Bluetooth device and read its model number:
 
     asyncio.run(main(address))
 
+DO NOT NAME YOUR SCRIPT `bleak.py`! It will cause a circular import error.
 
 See examples folder for more code, for instance example code for connecting to a
 `TI SensorTag CC2650 <http://www.ti.com/ww/en/wireless_connectivity/sensortag/>`_

docs/scanning.rst

@@ -22,6 +22,8 @@ To discover Bluetooth devices that can be connected to:
 
     asyncio.run(main())
 
+.. warning:: Do not name your script `bleak.py`! It will cause a circular import error.
+
 This will scan for 5 seconds and then produce a printed list of detected devices::
 
     24:71:89:CC:09:05: CC2650 SensorTag

docs/troubleshooting.rst

@@ -4,6 +4,17 @@ Troubleshooting
 
 When things don't seem to be working right, here are some things to try.
 
+---------------
+Common Mistakes
+---------------
+
+Many people name their first script ```bleak.py``. This causes the script to
+crash with an ``ImportError`` similar to::
+
+    ImportError: cannot import name 'BleakClient' from partially initialized module 'bleak' (most likely due to a circular import) (bleak.py)`
+
+To fix the error, change the name of the script to something other than ``bleak.py``.
+
 
 --------------
 Enable Logging

docs/usage.rst

@@ -52,6 +52,8 @@ or one can do it without the context manager like this:
 
     asyncio.run(main(address))
 
+.. warning:: Do not name your script `bleak.py`! It will cause a circular import error.
+
 Make sure you always get to call the disconnect method for a client before discarding it;
 the Bluetooth stack on the OS might need to be cleared of residual data which is cached in the
 ``BleakClient``.