document nrfutil python 3.9 workaround

embedded-workshop-book/src/installation.md

@@ -223,6 +223,71 @@ $ nrfutil version
 nrfutil version 6.1.0
 ```
 
+**NOTE** as of version 6.1.0 nrfutil indicates that it does "not" support Python 3.9 in its pip manifest. Due to this, the above `pip install` command will fail if you have a Python 3.9 interpreter installed. Here's how to work around the issue:
+
+*start of nrfutil python 3.9 workaround*
+
+``` console
+$ # these steps can also be done via a graphical interface
+
+$ # fetch the source code of version 6.1.0
+$ # or instead of curl you can enter the URL into your web browser
+$ curl -LO https://github.com/NordicSemiconductor/pc-nrfutil/archive/v6.1.zip
+
+$ # unzip the code
+$ unzip v6.1.zip
+
+$ # go into the new folder
+$ cd pc-nrfutil-6.1
+```
+
+Apply the following 2 patches (can also be done manually by editing these 2 files: `requirements.txt` and `setup.py`)
+
+``` diff
+--- a/requirements.txt  2021-01-05 10:50:12.611556607 +0100
++++ b/requirements.txt  2021-01-05 10:50:09.718226891 +0100
+@@ -4,7 +4,7 @@
+ ecdsa
+ intelhex
+ libusb1
+-pc_ble_driver_py >= 0.14.2
++# pc_ble_driver_py >= 0.14.2
+ piccata
+ protobuf
+ pyserial
+```
+
+``` diff
+--- a/setup.py  2021-01-05 10:49:56.014910707 +0100
++++ b/setup.py  2021-01-05 10:50:26.004873175 +0100
+@@ -148,7 +148,7 @@
+                      '../libusb/x86/libusb-1.0.dll', '../libusb/x64/libusb-1.0.dll',
+                      '../libusb/x64/libusb-1.0.dylib', '../libusb/LICENSE']
+     },
+-    python_requires='>=3.6, <3.9',
++    python_requires='>=3.6, <3.10',
+     install_requires=reqs,
+     zipfile=None,
+     tests_require=[
+```
+
+``` console
+$ patch -p1 < requirements.patch
+$ patch -p1 < setup.patch
+```
+
+Then install the patched `nrfutil`
+
+``` console
+$ pip install .
+
+$ # verify installation
+$ nrfutil version
+nrfutil version 6.1.0
+```
+
+*end of nrfutil python 3.9 workaround*
+
 ### `nrf-recover`
 
 Some nRF52840 devices, specially older revisions, may have parts of their Flash memory locked. To unlock the memory use the [`nrf-recover`](https://crates.io/crates/nrf-recover) tool.
@@ -235,4 +300,4 @@ $ cargo install nrf-recover
 $ nrf-recover -y
 Starting mass erase...
 Mass erase completed, chip unlocked
-```
+```