SqlSetup: Problem doing cluster install when SourePath is an UNC path

Details of the scenario you try and problem that is occurring:
This is a problem when SourcePath is an UNC share when doing cluster install.

Three scenarios I tried to get cluster install. Credentials parameters involved SetupCredential, SourceCredential and PsDscRunAsCredential. Only Scenario 3 worked.

Scenario 1.

Using only parameter SetupCredential. It is not allow to access the UNC path becuase it is running as SYSTEM.

VERBOSE: [SQLTEST4]:                            [[xSQLServerSetup]InstallSQL2014Instance] 2017-02-26_10-27-07: Using path: \\fileserver.company.local\images\SQL2014SP1-ENT\setup.exe
Access is denied

Scenario 2.

Using both parameter PsDscRunAsCredential, to access the UNC share, and parameter SetupCredential, because the setup.exe process is started using these credentials. But those credential in PsDscRunAsCredential did not have rights (to impersonate) so the setup.exe process could start and failed with error "The process could not be created. Create process as user error #1314".

VERBOSE: [SQLTEST4]: LCM:  [ End    Set      ]  [[xSQLServerSetup]InstallSQL2014Instance]  in 2.2910 seconds.
PowerShell DSC resource MSFT_xSQLServerSetup  failed to execute Set-TargetResource functionality with error message: Exception calling "CreateProcessAsUser" with "4" argument(s): "The process could not be created. Create process as user error #1314" 
    + CategoryInfo          : InvalidOperation: (:) [], CimException
    + FullyQualifiedErrorId : ProviderOperationExecutionFailure
    + PSComputerName        : sqltest4.company.local

It is a guess that is the rights that are the problem, but if it is there might be a workaround to give those permissions, see this article http://stackoverflow.com/questions/1475577/createprocessasuser-error-1314.

Scenario 3.

Using both parameter SourceCredential, to copy media locally, and parameter `SetupCredential, because the setup.exe process is started using these credentials.
This scenario worked!

VERBOSE: [SQLTEST4]:                            [[xSQLServerSetup]InstallSQL2014Instance] 2017-02-26_10-47-30: Process matching path 'C:\Windows\TEMP\SQL2014SP1-ENT\setup.exe' started in process ID 7024

The DSC configuration that is using the resource (as detailed as possible):
Configuration from working scenario 3.

xSQLServerSetup $resourceConfigName
{
    Action = 'InstallFailoverCluster'
    ForceReboot = $false

    SourcePath = '\\fileserver.company.local\images\SQL2014SP1-ENT'
    UpdateEnabled = 'False'

    SetupCredential = $SqlInstallCredential
    SourceCredential = $SqlInstallCredential

    InstanceName = 'SQL2014'
    Features = 'SQLENGINE,SSMS,ADV_SSMS'

    InstallSharedDir = 'C:\Program Files\Microsoft SQL Server'
    InstallSharedWOWDir = 'C:\Program Files (x86)\Microsoft SQL Server'
    InstanceDir = 'C:\Program Files\Microsoft SQL Server'

    SQLCollation = 'Finnish_Swedish_CI_AS'
    SQLSvcAccount = $SqlServiceCredential
    AgtSvcAccount = $SqlAgentServiceCredential
    SQLSysAdminAccounts = 'COMPANY\SQL Administrators', $SqlAdministratorCredential.UserName

    InstallSQLDataDir = 'G:\MSSQL\Data'
    SQLUserDBDir = 'E:\MSSQL\Data'
    SQLUserDBLogDir = 'F:\MSSQL\Log'
    SQLTempDBDir = 'H:\MSSQL\Temp'
    SQLTempDBLogDir = 'H:\MSSQL\Temp'
    SQLBackupDir = 'I:\MSSQL\Backup'

    FailoverClusterNetworkName = 'TESTCLU01'
    FailoverClusterIPAddress = '192.168.0.10'
    FailoverClusterGroupName = 'TESTCLU01A'

    DependsOn = '[WindowsFeature]NetFramework35','[WindowsFeature]NetFramework45'
}

Version of the Operating System, SQL Server and PowerShell the DSC Target Node is running:
Windows Server 2016, SQL Server 2014, PowerShell 5.0

Version of the DSC module you're using, or 'dev' if you're using current dev branch:
Dev

Start at the xSQLServerSetup InstallSQL2014Instance entry point and reproduce the cluster installation with SourcePath set to the UNC share and the three credential combinations described. Trace how SourceCredential, SetupCredential, and PsDscRunAsCredential are used, then verify the expected behavior with a regression test or clearly documented limitation.