Cryptic error message when Visual Studio is not installed

[olegsych]

• Install-PoshVs succeeds silently when Visual Studio is not installed.
• Import-VisualStudioEnvironment displays a cryptic error message if Visual Studio is not installed.

Import-BatchEnvironment : Cannot bind argument to parameter 'batchFile' because it is an empty string.
At C:\Users\olegsych\Documents\WindowsPowerShell\Modules\posh-vs\0.2.1\posh-vs.psm1:62 char:29
+     Import-BatchEnvironment $batchFile
+                             ~~~~~~~~~~
    + CategoryInfo          : InvalidData: (:) [Import-BatchEnvironment], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationErrorEmptyStringNotAllowed,Import-BatchEnvironment