Set the current culture to English in tests

Exception messages were being formatted with the machine culture.

src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs

@@ -117,6 +117,7 @@ public void XmlMemoryMapped()
             Assert.Equal("", outWriter.ToString());
 
             var xmlPath = Path.Combine(dir.Path, docName);
+            using (new EnsureEnglishUICulture())
             using (var fileStream = new FileStream(xmlPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
             using (var mmf = MemoryMappedFile.CreateFromFile(fileStream, "xmlMap", 0, MemoryMappedFileAccess.Read, HandleInheritability.None, leaveOpen: true))
             {

src/Compilers/VisualBasic/Test/CommandLine/CommandLineTests.vb

@@ -72,12 +72,14 @@ End Class")
             Assert.Equal("", outWriter.ToString())
 
             Dim xmlPath = Path.Combine(dir.Path, docName)
-            Using fileStream = New FileStream(xmlPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)
-                Using mmf = MemoryMappedFile.CreateFromFile(fileStream, "xmlMap", 0, MemoryMappedFileAccess.Read, HandleInheritability.None, leaveOpen:=True)
-                    exitCode = cmd.Run(outWriter)
-                    Assert.Equal(1, exitCode)
-                    Assert.Equal($"vbc : error BC2012: can't open '{xmlPath}' for writing: The requested operation cannot be performed on a file with a user-mapped section open.",
-            outWriter.ToString().Replace(Environment.NewLine, ""))
+            Using New EnsureEnglishUICulture()
+                Using fileStream = New FileStream(xmlPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)
+                    Using mmf = MemoryMappedFile.CreateFromFile(fileStream, "xmlMap", 0, MemoryMappedFileAccess.Read, HandleInheritability.None, leaveOpen:=True)
+                        exitCode = cmd.Run(outWriter)
+                        Assert.Equal(1, exitCode)
+                        Assert.Equal($"vbc : error BC2012: can't open '{xmlPath}' for writing: The requested operation cannot be performed on a file with a user-mapped section open.",
+                outWriter.ToString().Replace(Environment.NewLine, ""))
+                    End Using
                 End Using
             End Using
         End Sub