image.py: make device paths work with cmd_flash() again, add dd debug output

flash.py

@@ -18,9 +18,9 @@ ROOTFS = FLASH_PARTS['ROOTFS']
 
 @click.command(name='flash')
 @click.argument('what', type=click.Choice(list(FLASH_PARTS.values())))
-@click.argument('location', required=False, type=click.Choice(LOCATIONS))
-def cmd_flash(what, location):
-    """Flash a partition onto a device"""
+@click.argument('location', type=str, required=False)
+def cmd_flash(what: str, location: str):
+    """Flash a partition onto a device. `location` takes either a path to a block device or one of emmc, sdcard"""
     enforce_wrap()
     device, flavour = get_device_and_flavour()
     device_image_name = get_image_name(device, flavour)

image.py

@@ -23,7 +23,7 @@ IMG_FILE_BOOT_DEFAULT_SIZE = "90M"
 
 
 def dd_image(input: str, output: str, blocksize='1M') -> CompletedProcess:
-    return subprocess.run([
+    cmd = [
         'dd',
         f'if={input}',
         f'of={output}',
@@ -32,7 +32,9 @@ def dd_image(input: str, output: str, blocksize='1M') -> CompletedProcess:
         'oflag=direct',
         'status=progress',
         'conv=sync,noerror',
-    ])
+    ]
+    logging.debug(f'running dd cmd: {cmd}')
+    return subprocess.run(cmd)
 
 
 def partprobe(device: str):