Why doesn't ceph-deploy see Python?

Question

linux

Ubuntu Server 16.04.3 LTS, ceph-deploy 1.5.38. Passwordless login to the ceph1 node is configured.
When I try to create a new ceph-deploy new ceph1 config, I get

[ceph_deploy.conf][DEBUG ] found configuration file at: /home/cephuser/.cephdeploy.conf
[ceph_deploy.cli][INFO ] Invoked (1.5.38): /usr/bin/ceph-deploy new ceph1
[ceph_deploy. cli][INFO ] ceph-deploy options:
[ceph_deploy.cli][INFO ] username : None
[ceph_deploy.cli][INFO ] verbose : False
[ceph_deploy.cli][INFO ] overwrite_conf : False
[ceph_deploy.cli][INFO ] quiet : False
[ceph_deploy.cli][INFO ] cd_conf :
[ceph_deploy.cli][INFO ] cluster : ceph
[ceph_deploy.cli][INFO ] ssh_copykey : True
[ceph_deploy.cli][INFO ] mon : ['ceph1']
[ceph_deploy.cli][INFO ] func :
[ceph_deploy.cli][INFO ] public_network : None
[ceph_deploy.cli][INFO ] ceph_conf : None
[ceph_deploy. cli][INFO ] cluster_network : None
[ceph_deploy.cli][INFO ] default_release : False
[ceph_deploy.cli][INFO ] fsid : None
[ceph_deploy.new][DEBUG ] Creating new cluster named ceph
[ceph_deploy.new][INFO ] making sure passwordless SSH succeeds
[ceph1][DEBUG ] connected to host: ceph-deploy
[ceph1][INFO ] Running command: ssh -CT -o BatchMode=yes ceph1
sh: 1: python2: not found
[ceph_deploy][ERROR ] RuntimeError: connecting to host: ceph1 resulted in errors: IOError cannot send (already closed?)

Trying to install python-minimal - getting

sudo apt-get install python-minimal
Reading package lists... Done
Building dependency tree
Reading status information... Done
The newest version (2.7.11-1) of the python-minimal package is already installed.
0 updated, 0 new packages installed, 0 packages marked for removal, and 14 packages not updated.