ls: mmcblk*: No such file or directory

Host OS: Windows 10 Professional 15063.674
Device: Moto Z (aka `griffin` aka `XT1650-05`), China model
Output of `tetherback --verbose`:
```
tetherback v0.9.1
Found ADB version 1.0.39
Using default transfer method: adb exec-out pipe (--exec-out)
Device reports kernel 3.18.31-perf-g661294a-dirty
Device reports TWRP version 3.1.1-0
ls: mmcblk*: No such file or directory
Traceback (most recent call last):
File "C:\Users\[username removed]\AppData\Local\Programs\Python\Python36-32\Scripts\tetherback-script.py", line 11, in
load_entry_point('tetherback==0.9.1', 'console_scripts', 'tetherback')()
File "c:\users\[username removed]\appdata\local\programs\python\python36-32\lib\site-packages\tetherback\tetherback.py", line 322, in main
partmap = build_partmap(adb)
File "c:\users\[username removed]\appdata\local\programs\python\python36-32\lib\site-packages\tetherback\tetherback.py", line 133, in build_partmap
mmcblks = adb.check_output(('shell','cd /sys/block; ls -d mmcblk*')).split()
File "c:\users\[username removed]\appdata\local\programs\python\python36-32\lib\site-packages\tetherback\adb_wrapper.py", line 35, in check_output
return sp.check_output(self.adbcmd(adbargs), universal_newlines=un, **kwargs)
File "c:\users\[username removed]\appdata\local\programs\python\python36-32\lib\subprocess.py", line 336, in check_output
**kwargs).stdout
File "c:\users\[username removed]\appdata\local\programs\python\python36-32\lib\subprocess.py", line 418, in run
output=stdout, stderr=stderr)
subprocess.CalledProcessError: Command '('adb', '-d', 'shell', 'cd /sys/block; ls -d mmcblk*')' returned non-zero exit status 1.
```
Output of `adb shell mount`:
```
rootfs on / type rootfs (rw,seclabel,size=1819536k,nr_inodes=454884)
tmpfs on /dev type tmpfs (rw,seclabel,nosuid,relatime,size=1917320k,nr_inodes=479330,mode=755)
devpts on /dev/pts type devpts (rw,seclabel,relatime,mode=600)
proc on /proc type proc (rw,relatime,gid=3009,hidepid=2)
sysfs on /sys type sysfs (rw,seclabel,relatime)
selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime)
tmpfs on /tmp type tmpfs (rw,seclabel,relatime,size=1917320k,nr_inodes=479330)
pstore on /sys/fs/pstore type pstore (rw,seclabel,relatime)
adb on /dev/usb-ffs/adb type functionfs (rw,relatime)
/dev/block/sda19 on /cache type ext4 (rw,seclabel,relatime,data=ordered)
/dev/block/dm-0 on /data type f2fs (rw,seclabel,relatime,background_gc=on,user_xattr,acl,inline_data,extent_cache,active_logs=6)
/dev/block/dm-0 on /sdcard type f2fs (rw,seclabel,relatime,background_gc=on,user_xattr,acl,inline_data,extent_cache,active_logs=6)
/dev/block/sda15 on /system type ext4 (rw,seclabel,relatime,data=ordered)
```
Output of `adb shell "ls /sys/block"`:
```
dm-0
loop0
loop1
loop2
loop3
loop4
loop5
loop6
loop7
ram0
ram1
ram10
ram11
ram12
ram13
ram14
ram15
ram2
ram3
ram4
ram5
ram6
ram7
ram8
ram9
sda
sdb
sdc
sdd
zram0
```
Not sure why these blocks aren't starting with "mmcblk", but this could be a problem.