Hi, 
I'm testing the CLI tool, and I found 3.0alpha segfault always in a similar way, with various *.kra files tested: 

To reproduce:
===========
~$ krita --export test.kra --export-filename test.png

Result/Log
=========
QCoreApplication::arguments: Please instantiate the QApplication object first
krita.lib.pigment: Compiled for arch: ::Vc::SSE41Impl
krita.lib.pigment: Features supported:
krita.lib.pigment: 	 "SSE2" 	---	 yes
krita.lib.pigment: 	 "SSSE3" 	---	 yes
krita.lib.pigment: 	 "SSE4.1" 	---	 yes
krita.lib.pigment: 	 "AVX " 	---	 no
Set style "Fusion"
Setting XDG_DATA_DIRS "/home/deevad/Sources/krita/inst/bin/../share:/usr/share/cinnamon:/usr/share/gnome:/usr/local/share/:/usr/share/:/var/lib/snappy/desktop"
Available translations QSet("en_US")
Available domain translations QSet("en_US")
KoJsonTrader will load its plugins from "/home/deevad/Sources/krita/inst/lib/x86_64-linux-gnu/kritaplugins"
krita.general: "[\n0: /home/deevad/Sources/krita/inst/lib/x86_64-linux-gnu/libkritaglobal.so.15(kisBacktrace()+0x48) [0x7f709fc99108]\n1: /home/deevad/Sources/krita/inst/lib/x86_64-linux-gnu/kritaplugins/kritapngexport.so(+0xc8e3) [0x7f706836b8e3]\n2: /home/deevad/Sources/krita/inst/lib/x86_64-linux-gnu/kritaplugins/kritapngexport.so(+0x872c) [0x7f706836772c]\n3: /home/deevad/Sources/krita/inst/lib/x86_64-linux-gnu/libkritaui.so.15(+0x4fb500) [0x7f70a5554500]\n4: /home/deevad/Sources/krita/inst/lib/x86_64-linux-gnu/libkritaui.so.15(KisFilterChain::invokeChain()+0x115) [0x7f70a5553725]\n5: /home/deevad/Sources/krita/inst/lib/x86_64-linux-gnu/libkritaui.so.15(KisImportExportManager::exportDocument(QString const&, QByteArray&)+0x2dd) [0x7f70a555a0ad]\n6: /home/deevad/Sources/krita/inst/lib/x86_64-linux-gnu/libkritaui.so.15(KisApplication::start(KisApplicationArguments const&)+0x9a3) [0x7f70a55344c3]\n7: krita(main+0x8ad) [0x40461d]\n8: /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf1) [0x7f70a30f8841]\n9: krita(_start+0x29) [0x404fc9]\n]\n"
Segmentation fault