(#27) add try finally around directory changes

Co-Authored-By: James Ruskin <github@justpowerdown.com>

.appveyor.yml

@@ -99,10 +99,14 @@ build_script:
                     Write-Host ("{0}`n{1}`n" -f ('-'*60), "PACKAGE: $package")
                     $package_dir = ls -recurse | ? { $_.Name -eq "$package.nuspec"} | select -First 1 | % Directory
                     if (!$package_dir) { Write-Warning "Can't find package '$package'"; continue }
-                    pushd $package_dir
+                    try {
+                      pushd $package_dir
                       if (Test-Path update.ps1 -ea 0) { ./update.ps1 }
-                      choco pack; Push-Package;
-                    popd
+                      choco pack
+                      Push-Package
+                    } finally {
+                      popd
+                    }
                 }
                 return
             }