Error when exporting OBJ unattended

When doing an unattended OBJ export with python. The export will fail and give the atteched callstack.

Based on reprosteps provided in the UDN link

1. Open UE4 Editor, save a level in the content browser
2. Create a python scrip exporting the level asset to OBJ. [Link Removed] is an example of python script Loading the level "TestMap" in the content browser and exporting it to "C:
   FBX_Files
   Python Scripts - Import Export
   FolderTmp
   ExportedOBJ.obj".
3. In UE4 Editor, run the python script.

Expected: There should be no dialog window opening since we are running an automated script.
Actual: A dialog window asking for material export option open up (or if running unattended, tries to open and causes a crash).

[2020.11.25-23.13.09:726][ 0]Message Dialog was triggered in unattended script mode without a default value. 4 will be used.
[2020.11.25-23.13.09:736][ 0]LogOutputDevice: Error: === FDebug::DumpStackTrace(): ===
[2020.11.25-23.13.09:736][ 0]LogOutputDevice: Error: === FDebug::DumpStackTrace(): ===
[2020.11.25-23.13.09:736][ 0]LogOutputDevice: Error:
[2020.11.25-23.13.09:736][ 0]LogOutputDevice: Error:
[2020.11.25-23.13.09:736][ 0]LogOutputDevice: Error: [Callstack] 0x00007fe374c199ff libUE4Editor-UnrealEd.so!ULevelExporterOBJ::ExportText(FExportObjectInnerContext const*, UObject*, char16_t const*, FOutputDevice&, FFeedbackContext*, unsigned int) [/user_data/RND/dev/github-unrealengine-installed-build/Engine/Source/Editor/UnrealEd/Private/EditorExporters.cpp:1386]
[2020.11.25-23.13.09:736][ 0]LogOutputDevice: Error: [Callstack] 0x00007fe374c199ff libUE4Editor-UnrealEd.so!ULevelExporterOBJ::ExportText(FExportObjectInnerContext const*, UObject*, char16_t const*, FOutputDevice&, FFeedbackContext*, unsigned int) [/user_data/RND/dev/github-unrealengine-installed-build/Engine/Source/Editor/UnrealEd/Private/EditorExporters.cpp:1386]
[2020.11.25-23.13.09:736][ 0]LogOutputDevice: Error: [Callstack] 0x00007fe37a146399 libUE4Editor-Engine.so!UExporter::ExportToOutputDevice(FExportObjectInnerContext const*, UObject*, UExporter*, FOutputDevice&, char16_t const*, int, unsigned int, bool, UObject*) [/user_data/RND/dev/github-unrealengine-installed-build/Engine/Source/Runtime/Engine/Private/UnrealExporter.cpp:200]
[2020.11.25-23.13.09:736][ 0]LogOutputDevice: Error: [Callstack] 0x00007fe37a146399 libUE4Editor-Engine.so!UExporter::ExportToOutputDevice(FExportObjectInnerContext const*, UObject*, UExporter*, FOutputDevice&, char16_t const*, int, unsigned int, bool, UObject*) [/user_data/RND/dev/github-unrealengine-installed-build/Engine/Source/Runtime/Engine/Private/UnrealExporter.cpp:200]
[2020.11.25-23.13.09:737][ 0]LogOutputDevice: Error: [Callstack] 0x00007fe37a1473cb libUE4Editor-Engine.so!UExporter::RunAssetExportTask(UAssetExportTask*) [/user_data/RND/dev/github-unrealengine-installed-build/Engine/Source/Runtime/Engine/Private/UnrealExporter.cpp:301]
[2020.11.25-23.13.09:737][ 0]LogOutputDevice: Error: [Callstack] 0x00007fe37a1473cb libUE4Editor-Engine.so!UExporter::RunAssetExportTask(UAssetExportTask*) [/user_data/RND/dev/github-unrealengine-installed-build/Engine/Source/Runtime/Engine/Private/UnrealExporter.cpp:301]
[2020.11.25-23.13.09:737][ 0]LogOutputDevice: Error: [Callstack] 0x00007fe37a3a97f0 libUE4Editor-Engine.so!UExporter::execRunAssetExportTask(UObject*, FFrame&, void*) [/user_data/RND/dev/github-unrealengine-installed-build/Engine/Intermediate/Build/Linux/B4D820EA/UE4Editor/Inc/Engine/Exporter.gen.cpp:38]
[2020.11.25-23.13.09:737][ 0]LogOutputDevice: Error: [Callstack] 0x00007fe37a3a97f0 libUE4Editor-Engine.so!UExporter::execRunAssetExportTask(UObject*, FFrame&, void*) [/user_data/RND/dev/github-unrealengine-installed-build/Engine/Intermediate/Build/Linux/B4D820EA/UE4Editor/Inc/Engine/Exporter.gen.cpp:38]
[2020.11.25-23.13.09:737][ 0]LogOutputDevice: Error: [Callstack] 0x00007fe37b708a9c libUE4Editor-CoreUObject.so!UFunction::Invoke(UObject*, FFrame&, void*) [/user_data/RND/dev/github-unrealengine-installed-build/Engine/Source/Runtime/CoreUObject/Private/UObject/Class.cpp:5542]
[2020.11.25-23.13.09:737][ 0]LogOutputDevice: Error: [Callstack] 0x00007fe37b708a9c libUE4Editor-CoreUObject.so!UFunction::Invoke(UObject*, FFrame&, void*) [/user_data/RND/dev/github-unrealengine-installed-build/Engine/Source/Runtime/CoreUObject/Private/UObject/Class.cpp:5542]
[2020.11.25-23.13.09:737][ 0]LogOutputDevice: Error: [Callstack] 0x00007fe37b93e0fd libUE4Editor-CoreUObject.so!UObject::ProcessEvent(UFunction*, void*) [/user_data/RND/dev/github-unrealengine-installed-build/Engine/Source/Runtime/CoreUObject/Private/UObject/ScriptCore.cpp:1914]
[2020.11.25-23.13.09:737][ 0]LogOutputDevice: Error: [Callstack] 0x00007fe37b93e0fd libUE4Editor-CoreUObject.so!UObject::ProcessEvent(UFunction*, void*) [/user_data/RND/dev/github-unrealengine-installed-build/Engine/Source/Runtime/CoreUObject/Private/UObject/ScriptCore.cpp:1914]
[2020.11.25-23.13.09:737][ 0]LogOutputDevice: Error: [Callstack] 0x00007fe305165f17 libUE4Editor-PythonScriptPlugin.so!PyUtil::InvokeFunctionCall(UObject*, UFunction const*, void*, char16_t const*) [/user_data/RND/dev/github-unrealengine-installed-build/Engine/Plugins/Experimental/PythonScriptPlugin/Source/PythonScriptPlugin/Private/PyUtil.cpp:577]
...
[2020.11.25-23.13.19:830][ 0]LogOutputDevice: Error:
[2020.11.25-23.13.19:830][ 0]LogOutputDevice: Error:
[2020.11.25-23.13.19:833][ 0]Message dialog closed, result: Cancel, title: Message, text: Would you like to export the materials as images (slower)?
[2020.11.25-23.13.19:837][ 0]LogFileManager: Warning: MoveFile was unable to move '/user_data/.tmp/UnrealExportFile.tmp' to '/user_data/.tmp/unrealFbExport_vevKY6.obj' (Error Code 0), retrying in .5s...
[2020.11.25-23.13.19:837][ 0]LogFileManager: Warning: MoveFile was unable to move '/user_data/.tmp/UnrealExportFile.tmp' to '/user_data/.tmp/unrealFbExport_vevKY6.obj' (Error Code 0), retrying in .5s...
[2020.11.25-23.13.20:338][ 0]LogFileManager: Warning: MoveFile was unable to move '/user_data/.tmp/UnrealExportFile.tmp' to '/user_data/.tmp/unrealFbExport_vevKY6.obj' (Error Code 0), retrying in .5s...
[2020.11.25-23.13.20:338][ 0]LogFileManager: Warning: MoveFile was unable to move '/user_data/.tmp/UnrealExportFile.tmp' to '/user_data/.tmp/unrealFbExport_vevKY6.obj' (Error Code 0), retrying in .5s...
[2020.11.25-23.13.20:842][ 0]LogFileManager: Warning: MoveFile was unable to move '/user_data/.tmp/UnrealExportFile.tmp' to '/user_data/.tmp/unrealFbExport_vevKY6.obj' (Error Code 0), retrying in .5s...