This is a common crash affecting users in 4.15 and 4.16. It appears to often occur while editing static meshes.
User Descriptions
Source Context
375 {
376 FString FailureReason;
377 FString Result;
378 if (!TryConvertLongPackageNameToFilename(InLongPackageName, Result, InExtension))
379 {
380 ***** UE_LOG(LogPackageName, Fatal,TEXT("LongPackageNameToFilename failed to convert '%s'. Path does not map to any roots."), *InLongPackageName);
381 }
382 return Result;
383 }
repro steps currently unknown
Fatal error: [File:D:\Build\++UE4+Release-4.15+Compile\Sync\Engine\Source\Runtime\CoreUObject\Private\Misc\PackageName.cpp] [Line: 381] LongPackageNameToFilename failed to convert 'None'. Path does not map to any roots. UE4Editor_CoreUObject!FPackageName::LongPackageNameToFilename() [packagename.cpp:381] UE4Editor_ContentBrowser!ContentBrowserUtils::GetPackageLengthForCooking() [contentbrowserutils.cpp:1747] UE4Editor_ContentBrowser!SAssetViewItem::CreateToolTipWidget() [assetviewwidgets.cpp:682] UE4Editor_ContentBrowser!SAssetViewItemToolTip::OnOpening() [assetviewwidgets.cpp:261] UE4Editor_Slate!FSlateApplication::UpdateToolTip() [slateapplication.cpp:3539] UE4Editor_Slate!FSlateApplication::ProcessMouseMoveEvent() [slateapplication.cpp:5713] UE4Editor_Slate!FSlateApplication::OnMouseMove() [slateapplication.cpp:5663] UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() [windowsapplication.cpp:1739] UE4Editor_Core!FWindowsApplication::DeferMessage() [windowsapplication.cpp:2120] UE4Editor_Core!FWindowsApplication::ProcessMessage() [windowsapplication.cpp:867] UE4Editor_Core!FWindowsApplication::AppWndProc() [windowsapplication.cpp:714] user32!UserCallWinProcCheckWow() user32!DispatchMessageWorker() UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() [windowsplatformmisc.cpp:980] UE4Editor!FEngineLoop::Tick() [launchengineloop.cpp:2977] UE4Editor!GuardedMain() [launch.cpp:166] UE4Editor!GuardedMainWrapper() [launchwindows.cpp:134] UE4Editor!WinMain() [launchwindows.cpp:210] UE4Editor!__scrt_common_main_seh() [exe_common.inl:264] kernel32!BaseThreadInitThunk() ntdll!RtlUserThreadStart()
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-47246 in the post.