I also experience the same thing on Ubuntu 14.04.3 LTS using Ansible 2.0.0.2-1ppa~trusty.
sysadm@controller:~$ ansible -vvv host1 -m command -a 'ls -l /'
Using /etc/ansible/ansible.cfg as config file
<10.10.10.51> ESTABLISH SSH CONNECTION FOR USER: None
<10.10.10.51> SSH: EXEC ssh -C -q -o ControlMaster=auto -o ControlPersist=60s -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=10 -o ControlPath=/home/sysadm/.ansible/cp/ansible-ssh-%h-%p-%r -tt 10.10.10.51 '( umask 22 && mkdir -p "$( echo $HOME/.ansible/tmp/ansible-tmp-1455084832.33-184704261198709 )" && echo "$( echo $HOME/.ansible/tmp/ansible-tmp-1455084832.33-184704261198709 )" )'
10.10.10.51 | FAILED | rc=0 >>
ERROR! failed to resolve remote temporary directory from ansible-tmp-1455084832.33-184704261198709: `( umask 22 && mkdir -p "$( echo $HOME/.ansible/tmp/ansible-tmp-1455084832.33-184704261198709 )" && echo "$( echo $HOME/.ansible/tmp/ansible-tmp-1455084832.33-184704261198709 )" )` returned empty string
sysadm@controller:~$ ansible -vvv host1 -m command -a 'ls -l /'
Using /etc/ansible/ansible.cfg as config file
<10.10.10.51> ESTABLISH SSH CONNECTION FOR USER: None
<10.10.10.51> SSH: EXEC ssh -C -q -o ControlMaster=auto -o ControlPersist=60s -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=10 -o ControlPath=/home/sysadm/.ansible/cp/ansible-ssh-%h-%p-%r -tt 10.10.10.51 '( umask 22 && mkdir -p "$( echo $HOME/.ansible/tmp/ansible-tmp-1455085172.76-47799942152084 )" && echo "$( echo $HOME/.ansible/tmp/ansible-tmp-1455085172.76-47799942152084 )" )'
<10.10.10.51> PUT /tmp/tmpMAqVn7 TO /home/sysadm/.ansible/tmp/ansible-tmp-1455085172.76-47799942152084/command
<10.10.10.51> SSH: EXEC sftp -b - -C -o ControlMaster=auto -o ControlPersist=60s -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=10 -o ControlPath=/home/sysadm/.ansible/cp/ansible-ssh-%h-%p-%r '[10.10.10.51]'
<10.10.10.51> ESTABLISH SSH CONNECTION FOR USER: None
<10.10.10.51> SSH: EXEC ssh -C -q -o ControlMaster=auto -o ControlPersist=60s -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=10 -o ControlPath=/home/sysadm/.ansible/cp/ansible-ssh-%h-%p-%r -tt 10.10.10.51 'LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8 /usr/bin/python /home/sysadm/.ansible/tmp/ansible-tmp-1455085172.76-47799942152084/command; rm -rf "/home/sysadm/.ansible/tmp/ansible-tmp-1455085172.76-47799942152084/" > /dev/null 2>&1'
10.10.10.51 | SUCCESS | rc=0 >>
total 84
drwxr-xr-x 2 root root 4096 Jan 18 04:41 bin
drwxr-xr-x 3 root root 4096 Jan 18 04:41 boot
drwxr-xr-x 15 root root 4040 Feb 10 06:06 dev
...
Any idea why this is happening?