Error in conversion for output format GTiff using SRTM

[scottstanie]

$ sardem --bbox -103.2 30.1 -103.1 30.2 --output-format GTiff -o dem.tif
[12/09 12:45:16] [INFO dem.py] Bounds: -103.2 30.1 -103.1 30.2
[12/09 12:45:16] [INFO download.py] /Users/staniewi/.cache/sardem/N30W104.hgt already exists, skipping.
[12/09 12:45:16] [INFO dem.py] Cropping stitched DEM to boundaries
[12/09 12:45:16] [INFO dem.py] Rate = 1: No upsampling to do
[12/09 12:45:16] [INFO dem.py] Writing DEM to dem.tif
[12/09 12:45:16] [INFO dem.py] Writing .dem.rsc file to dem.tif.rsc
[12/09 12:45:16] [INFO dem.py] Correcting DEM to heights above WGS84 ellipsoid
ERROR 4: `egm_dem.tif' not recognized as a supported file format.
[12/09 12:45:17] [ERROR conversions.py] Failed to convert DEM:
Traceback (most recent call last):
  File "/Users/staniewi/repos/sardem/sardem/conversions.py", line 89, in convert_dem_to_wgs84
    egm_to_wgs84(
  File "/Users/staniewi/repos/sardem/sardem/conversions.py", line 36, in egm_to_wgs84
    xsize, ysize = _get_size(filename)
  File "/Users/staniewi/repos/sardem/sardem/conversions.py", line 66, in _get_size
    xsize, ysize = ds.RasterXSize, ds.RasterYSize
AttributeError: 'NoneType' object has no attribute 'RasterXSize'
[12/09 12:45:17] [ERROR conversions.py] Reverting back, using EGM dem as output