This is the log
Spoiler:
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
calibre Log de Debug
calibre 3.21 embedded-python: False is64bit: True
Linux-4.15.0-38-generic-x86_64-with-Ubuntu-18.04-bionic Linux ('64bit', '')
('Linux', '4.15.0-38-generic', '#41-Ubuntu SMP Wed Oct 10 10:59:38 UTC 2018')
Python 2.7.15rc1
Linux: ('Ubuntu', '18.04', 'bionic')
Interface language: pt_BR
calibre 3.21 embedded-python: False is64bit: True
Linux-4.15.0-38-generic-x86_64-with-Ubuntu-18.04-bionic Linux ('64bit', '')
('Linux', '4.15.0-38-generic', '#41-Ubuntu SMP Wed Oct 10 10:59:38 UTC 2018')
Python 2.7.15rc1
Linux: ('Ubuntu', '18.04', 'bionic')
Interface language: pt_BR
Turning on automatic hidpi scaling
devicePixelRatio: 1.0
logicalDpi: 96.0 x 96.0
physicalDpi: 95.6235294118 x 95.5818815331
Using calibre Qt style: True
[0.00] Starting up...
[0.00] Showing splash screen...
[0.09] splash screen shown
[0.09] Initializing db...
[0.11] db initialized
[0.11] Constructing main UI...
Looking for desktop notifier support from: org.freedesktop.Notifications
org.freedesktop.Notifications found in 0.0 seconds
[0.52] main UI initialized...
[0.52] Hiding splash screen
*** BUG ***
In pixman_region32_init_rect: Invalid rectangle passed
Set a breakpoint on '_pixman_log_error' to debug
[5.41] splash screen hidden
[5.41] Started up in 5.41 seconds with 320 books