The command was found in the module PowerShellGet, but the module could not be loaded.

While testing a PowerShell DSC script deployed by Azure Automation on an Azure Virtual Machine I ran against the following error message: 

The command <command> was found in the module PowerShellGet, but the module could not be loaded.

What I tried to accomplish was automatically installing the PowerShell Az modules with the following PowerShell DSC script.

# Import DSC modules
Import-DscResource -ModuleName "PowerShellGet" -ModuleVersion 2.2.5

Node $AllNodes.NodeName
{
  PSModule "Az" {
    Ensure             = "Present"
    Name               = "Az"
    Repository         = "PSGallery"
    InstallationPolicy = "Trusted"
    AllowClobber       = $true
    Force              = $true
    RequiredVersion    = 5.6.0
  }
}

To solve this issue you also have to import the PackageManagement module because PowerShellGet has a dependency on this module. The correct version of the script is thus:

# Import DSC modules
Import-DscResource -ModuleName "PackageManagement" -ModuleVersion 1.4.4
Import-DscResource -ModuleName "PowerShellGet" -ModuleVersion 2.2.5

Node $AllNodes.NodeName
{
  PSModule "Az" {
    Ensure             = "Present"
    Name               = "Az"
    Repository         = "PSGallery"
    InstallationPolicy = "Trusted"
    AllowClobber       = $true
    Force              = $true
    RequiredVersion    = 5.6.0
  }
}

Update (March, 15th)

The PowerShellGet module has a specific dependency on version 1.4.4 of the PackageManagement module. You can see it defined in the manifest file (PowerShellGet.psd1).

RequiredModules   = @(@{ModuleName = 'PackageManagement'; ModuleVersion = '1.4.4' })