Python script terminates after calling QgsProject.write()

Python script using QGIS package terminates suddenly when calling QgsProject.write.
Idea is to create QGIS Project with select list of files and save it to disk, in automated manner.

Script:

from qgis.core import QgsProject, QgsRasterLayer

def foo():
    filePath = "C:/Users/username/Documents/projects/GeoTiffSample.tiff"
    savePAth = "C:/Users/username/Documents/projects/test2.qgs"
    proj = QgsProject.instance()
    proj.setFileName(savePAth)
    testlayer = QgsRasterLayer(filePath, baseName = "testLayer")
    proj.addMapLayer(testlayer)
    proj.setFileName(savePAth)
    proj.setDirty(True)
    try:
        print("Prewrite")
        ret = proj.write()
        print("Postwrite")
        pass
    except Exception as exc:
        print(exc)
    print(ret) 

print("START")
try:
    foo()
except Exception as exc:
    print(exc)
print("END")

Output:

START
Prewrite

Documentation is kind of lacking on any info. I suspect unhandeled exception in QGIS library.

from qgis.core import QgsProject, QgsRasterLayer, QgsApplication

#Optional line: QgsApplication.setPrefixPath("/path/to/qgis/installation", True)
#I don't have qgis installed and simply using pyqgis package, so line was ommited

qgs = QgsApplication([],True)
qgs.initQgis() #initiate QGIS

#Enter your code here

qgs.exitQgis() #free resources