QGIS » QGIS Application

Testing QGIS 3.0, KyngChaos QGIS 3.0.0-3 (because MacPorts QGIS 3.1 crashes under OSX))

Have DEM and using GRASS r.viewshed - which works with QGIS 2.18.15

With QGIS 3.0 and using the same DEM file, it ppears to execute but no output.
The runtime processing log display disappears too quickly to capture any info

with GRASS set to log everything
GRASS log shows:
2018-04-15T03:04:21 INFO processInputs end. Commands: ['g.proj -c proj4="+proj=tmerc +lat_0=42.5 +lon_0=-71.66666666666667 +k=0.999966667 +x_0=300000.0000000001 +y_0=0 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=us-ft +no_defs"', 'r.external input="/Users/garthfletcher/GPS MASON/CeremonialStones/Clipped_R_Ft_3614.tif" band=1 output="rast_5ad2f9755025c2" --overwrite -o', 'g.region n=183135.6038 s=-182403.73670000004 e=1165623.3353 w=893494.6569 res=29.682447469458985']
2018-04-15T03:04:21 INFO processCommands end. Commands: ['g.proj -c proj4="+proj=tmerc +lat_0=42.5 +lon_0=-71.66666666666667 +k=0.999966667 +x_0=300000.0000000001 +y_0=0 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=us-ft +no_defs"', 'r.external input="/Users/garthfletcher/GPS MASON/CeremonialStones/Clipped_R_Ft_3614.tif" band=1 output="rast_5ad2f9755025c2" --overwrite -o', 'g.region n=183135.6038 s=-182403.73670000004 e=1165623.3353 w=893494.6569 res=29.682447469458985', 'r.viewshed input=rast_5ad2f9755025c2 coordinates=955736.0695305177,98639.23656404298 [EPSG:3614] observer_elevation=1.75 target_elevation=0 max_distance=-1 refraction_coeff=0.14286 memory=500 output=outputae439ea3cb0049e2af26c672b5d51650 --overwrite']

By running r.viewshed in batch mode I can capture a bit more:
Log shows:

Processing algorithm 1/1…
Algorithm r.viewshed - Computes the viewshed of a point on an elevation raster map. starting…
Input parameters: {'-b': False, '-c': False, '-e': False, '-r': False, 'GRASS_RASTER_FORMAT_META': '', 'GRASS_RASTER_FORMAT_OPT': '', 'GRASS_REGION_CELLSIZE_PARAMETER': 0.0, 'GRASS_REGION_PARAMETER': None, 'coordinates': '955712.2255720419,98615.39260556722 [EPSG:3614]', 'input': 'Reprojected', 'max_distance': -1.0, 'memory': 500.0, 'observer_elevation': 1.75, 'output': <QgsProcessingOutputLayerDefinition {'sink':/Users/garthfletcher/Intervis.tif, 'createOptions': {}}>, 'refraction_coeff': 0.14286, 'target_elevation': 0.0}

g.proj -c proj4="+proj=tmerc +lat_0=42.5 +lon_0=-71.66666666666667 +k=0.999966667 +x_0=300000.0000000001 +y_0=0 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=us-ft +no_defs"
r.external input="/var/folders/h5/jbjhn4xs6x37xt_2m6x2nkbm0000gp/T/processing_a329705d8a9546dab23ecfad71acf014/fa50552226784df3a49e92e535ad542d/OUTPUT.tif" band=1 output="rast_5ad2f773129716" --overwrite -o
g.region n=183135.60382465608 s=-182403.7367341584 e=1165623.3352567302 w=893494.6568772573 res=29.682447467219998
r.viewshed input=rast_5ad2f773129716 coordinates=955712.2255720419,98615.39260556722 [EPSG:3614] observer_elevation=1.75 target_elevation=0 max_distance=-1 refraction_coeff=0.14286 memory=500 output=output754c53d8373344569ae52aa9ebd1fc0a --overwrite
g.region raster=output754c53d8373344569ae52aa9ebd1fc0a
r.out.gdal -t -m input="output754c53d8373344569ae52aa9ebd1fc0a" output="/Users/garthfletcher/Intervis.tif" format="GTiff" createopt="TFW=YES,COMPRESS=LZW" --overwrite
/var/folders/h5/jbjhn4xs6x37xt_2m6x2nkbm0000gp/T/processing_a329705d8a9546dab23ecfad71acf014/grassdata/temp_location/PERMANENT: /Applications/QGIS_3.app/Contents/MacOS/grass/etc/colors/grass: Permission denied
/var/folders/h5/jbjhn4xs6x37xt_2m6x2nkbm0000gp/T/processing_a329705d8a9546dab23ecfad71acf014/grassdata/temp_location/PERMANENT: /Applications/QGIS_3.app/Contents/MacOS/grass/etc/colors/grass: Permission denied
Algorithm r.viewshed - Computes the viewshed of a point on an elevation raster map. correctly executed…
Execution completed in 0.18 seconds
Results: {'output': <QgsProcessingOutputLayerDefinition {'sink':/Users/garthfletcher/Intervis.tif, 'createOptions': {}}>}

Loading resulting layers
Batch execution completed in 0.23 seconds

Note the above batch log includes:
"/Applications/QGIS_3.app/Contents/MacOS/grass/etc/colors/grass: Permission denied",

but there is a /Applications/QGIS_3.app/Contents/MacOS/grass/etc/colors/grass file and
changing its permissions to read/write for all has no effect.

I made sure that both DEM file and the display were using the same CRS.

Any ideas?