MLBEDSW-5912 - Update to Python 3.8

Change required python version from 3.6 to 3.8 in setup.py and allow
any python3 version for black pre-commit linting.

Signed-off-by: Rickard Bolin <rickard.bolin@arm.com>
Change-Id: I0d8936d92efd5137561834c0de1a3449f9e5f25c
diff --git a/Pipfile b/Pipfile
index 24e3e5e..eaf8ff8 100644
--- a/Pipfile
+++ b/Pipfile
@@ -4,9 +4,9 @@
 verify_ssl = true
 
 [dev-packages]
-pre-commit = "*"
-pytest = "*"
-pytest-cov = "*"
+pre-commit = "2.17.0"
+pytest = "6.2.5"
+pytest-cov = "3.0.0"
 ethos-u-vela = {editable = true,path = "."}
 
 [packages]