[yocto] ERROR: Unable to connect to bitbake server, or start one

[Gera Pesikoff]

Hi
I started to study bitbake and decided to repeat the BitBake Hello World from the
manual
(http://www.yoctoproject.org/docs/2.3.1/bitbake-user-manual/bitbake-user-manual.html#bitbake-hello-world).
I do everything according to the instructions, but when I run the bitbake
command, I get the following output:

NOTE: Retrying server connection... (Traceback (most recent call last):
File "/home/leonid/test/bitbake/lib/bb/main.py", line 432, in setup_bitbake
topdir, lock = lockBitbake()
File "/home/leonid/test/bitbake/lib/bb/main.py", line 484, in lockBitbake
lockfile = topdir + "/bitbake.lock"
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'
)

This is repeated five times, and at the end:

ERROR: Unable to connect to bitbake server, or start one

Could someone please tell me what the problem is and what I can do about it?
I'm using Kubuntu 17.04 and clear Ubuntu 17.04. BitBake Build Tool Core version
1.35.0
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