$ juju bootstrap --constraints instance-type=m3.small                                          
                                                              
Bootstrap failed, destroying environment
ERROR invalid constraint value: instance-type=m3.small
valid values are: [m1.small m1.medium m1.large m1.xlarge m3.medium m3.large m3.xlarge m3.2xlarge c1.medium c1.xlarge cc2.8xlarge c3.large c3.xlarge c3.
2xlarge c3.4xlarge c3.8xlarge cg1.4xlarge g2.2xlarge m2.xlarge m2.2xlarge m2.4xlarge cr1.8xlarge r3.large r3.xlarge r3.2xlarge r3.4xlarge r3.8xlarge hi
1.4xlarge i2.xlarge i2.2xlarge i2.4xlarge i2.8xlarge hs1.8xlarge t1.micro]