Here's what I did when trying to import an environment:

first I create the environment, by the same name as listed in //etc/puppet/environments:

# hammer environment create --name $environment

Next I try to import the classes, the following should work but fails:

# hammer proxy import-classes --environment $environment
Import of puppet classes failed:
  Missing arguments for 'id'

Next I try the following, which also should work, but once again fails:

# hammer proxy import-classes --environment $environment --id $id
Import of puppet classes failed:
  Resource smart_proxy not found by id '$id'

The only workaround is if I always set the id's value to "1", irrespective of which environment I want to import classes for:

# hammer proxy import-classes --environment $environment --id 1
Puppet classes were imported

So I believe we have 2 bugs, here. First the id parameter should be optional. Second, the id parameter if specified should be the correct value.

Here's the debug info:

[root@puppetmaster ~]# hammer -d proxy import-classes --environment $environment
[ INFO 2015-08-06 15:29:23 Init] Initialization of Hammer CLI (0.2.0) has started...
[DEBUG 2015-08-06 15:29:23 Init] Running at ruby 2.0.0-p598
[ INFO 2015-08-06 15:29:23 Init] Configuration from the file /etc/hammer/cli_config.yml has been loaded
[ INFO 2015-08-06 15:29:23 Init] Configuration from the file /etc/hammer/cli.modules.d/foreman.yml has been loaded
[ INFO 2015-08-06 15:29:23 Init] Configuration from the file /root/.hammer/cli.modules.d/foreman.yml has been loaded
[DEBUG 2015-08-06 15:29:23 Connection] Registered: foreman
[DEBUG 2015-08-06 15:29:23 API] Global headers: {
        :content_type => "application/json",
              :accept => "application/json;version=2",
    "Accept-Language" => "en_GB" 
}
[ INFO 2015-08-06 15:29:23 Modules] Extension module hammer_cli_foreman (0.2.0) loaded
[DEBUG 2015-08-06 15:29:23 Init] Using locale 'en_GB'
[DEBUG 2015-08-06 15:29:23 Init] 'mo' files for locale domain 'hammer-cli' loaded from '/usr/share/gems/gems/hammer_cli-
0.2.0/locale'
[DEBUG 2015-08-06 15:29:23 Init] 'mo' files for locale domain 'hammer-cli-foreman' loaded from '/usr/share/gems/gems/ham
mer_cli_foreman-0.2.0/locale'
[ INFO 2015-08-06 15:29:23 HammerCLI::MainCommand] Called with options: {"option_debug"=>true}
[ INFO 2015-08-06 15:29:23 HammerCLIForeman::SmartProxy] Called with options: {}
[ INFO 2015-08-06 15:29:23 HammerCLIForeman::SmartProxy::ImportPuppetClassesCommand] Called with options: {"option_envir
onment_name"=>"$environment"}
[ INFO 2015-08-06 15:29:23 API] GET /api/environments
[DEBUG 2015-08-06 15:29:23 API] Params: {
    :search => "name = \"$environment\"" 
}
[DEBUG 2015-08-06 15:29:23 API] Headers: {
    :params => {
        :search => "name = \"$environment\"" 
    }
}
[DEBUG 2015-08-06 15:29:24 API] Response: {
       "total" => 4,
    "subtotal" => 1,
        "page" => 1,
    "per_page" => 20,
      "search" => "name = \"$environment\"",
        "sort" => {
           "by" => nil,
        "order" => nil
    },
     "results" => [
        [0] {
            "created_at" => "2015-08-06T14:26:04Z",
            "updated_at" => "2015-08-06T14:26:04Z",
                  "name" => "$environment",
                    "id" => 7
        }
    ]
}
[DEBUG 2015-08-06 15:29:24 API] Response headers: {
                   :date => "Thu, 06 Aug 2015 14:29:23 GMT",
                 :server => "Apache/2.4.6 (CentOS)",
        :foreman_version => "1.8.2",
    :foreman_api_version => "2",
        :apipie_checksum => "296420cd159a1435d80a1a3e3a642264",
        :x_ua_compatible => "IE=Edge,chrome=1",
          :cache_control => "must-revalidate, private, max-age=0",
           :x_request_id => "23c3de7e18401d8a305e2c79da5ef2dd",
              :x_runtime => "0.061600",
           :x_rack_cache => "miss",
           :x_powered_by => "Phusion Passenger 4.0.18",
             :set_cookie => [
        [0] "_session_id=BAh7B0kiD3Nlc3Npb25faWQGOgZFRkkiJTAzMjYzNmIyNDRhMmU0MzY2NDA3MTIyYjBhZDg2YTM4BjsAVEkiC2xvY2FsZQY
7AEYiCmVuX0dC--6880435ecda38b8a9a2d684cb2fbf784c41a00b6; path=/; HttpOnly",
        [1] "request_method=; path=/; expires=Thu, 01-Jan-1970 00:00:00 GMT" 
    ],
                   :etag => "\"0aa26df58d42f93dfdaff5005d75d767\"",
                 :status => "200 OK",
             :connection => "close",
      :transfer_encoding => "chunked",
           :content_type => "application/json; charset=utf-8" 
}
[ERROR 2015-08-06 15:29:24 Exception] Missing arguments for 'id'
Import of puppet classes failed:
  Missing arguments for 'id'
[ERROR 2015-08-06 15:29:24 Exception]

ApipieBindings::MissingArgumentsError (Missing arguments for 'id'):
    /usr/share/gems/gems/apipie-bindings-0.0.13/lib/apipie_bindings/action.rb:63:in `validate!'
    /usr/share/gems/gems/apipie-bindings-0.0.13/lib/apipie_bindings/api.rb:159:in `call'
    /usr/share/gems/gems/apipie-bindings-0.0.13/lib/apipie_bindings/resource.rb:14:in `call'
    /usr/share/gems/gems/hammer_cli-0.2.0/lib/hammer_cli/apipie/command.rb:43:in `send_request'
    /usr/share/gems/gems/hammer_cli_foreman-0.2.0/lib/hammer_cli_foreman/commands.rb:185:in `send_request'
    /usr/share/gems/gems/hammer_cli-0.2.0/lib/hammer_cli/apipie/command.rb:34:in `execute'
    /usr/share/gems/gems/clamp-0.6.2/lib/clamp/command.rb:68:in `run'
    /usr/share/gems/gems/hammer_cli-0.2.0/lib/hammer_cli/abstract.rb:23:in `run'
    /usr/share/gems/gems/clamp-0.6.2/lib/clamp/subcommand/execution.rb:11:in `execute'
    /usr/share/gems/gems/clamp-0.6.2/lib/clamp/command.rb:68:in `run'
    /usr/share/gems/gems/hammer_cli-0.2.0/lib/hammer_cli/abstract.rb:23:in `run'
    /usr/share/gems/gems/clamp-0.6.2/lib/clamp/subcommand/execution.rb:11:in `execute'
    /usr/share/gems/gems/clamp-0.6.2/lib/clamp/command.rb:68:in `run'
    /usr/share/gems/gems/hammer_cli-0.2.0/lib/hammer_cli/abstract.rb:23:in `run'
    /usr/share/gems/gems/clamp-0.6.2/lib/clamp/command.rb:126:in `run'
    /usr/share/gems/gems/hammer_cli-0.2.0/bin/hammer:108:in `<top (required)>'
    /bin/hammer:23:in `load'
    /bin/hammer:23:in `<main>'