Clean up some error usage in mmap

Author: BCSharp

Src/IronPython.Modules/mmap.cs

@@ -807,7 +807,7 @@ public void resize(long newsize) {
                         // resize on Posix platforms
                         try {
                             if (_handle.IsInvalid) {
-                                throw PythonOps.OSError(PythonErrno.EBADF, "Bad file descriptor");
+                                throw PythonNT.GetOsError(PythonErrno.EBADF);
                             }
                             _view.Flush();
                             _view.Dispose();
@@ -1109,20 +1109,18 @@ internal Bytes GetSearchString() {
                 }
             }
 
-            [SupportedOSPlatform("linux"), SupportedOSPlatform("macos")]
+            [SupportedOSPlatform("linux")]
+            [SupportedOSPlatform("macos")]
             private static long GetFileSizeUnix(SafeFileHandle handle) {
                 long size;
                 if (handle.IsInvalid) {
-                    throw PythonOps.OSError(PythonExceptions._OSError.ERROR_INVALID_HANDLE, "Invalid file handle");
+                    throw PythonNT.GetOsError(PythonErrno.EBADF);
                 }
 
                 if (Mono.Unix.Native.Syscall.fstat((int)handle.DangerousGetHandle(), out Mono.Unix.Native.Stat status) == 0) {
                     size = status.st_size;
                 } else {
-                    Mono.Unix.Native.Errno errno = Mono.Unix.Native.Stdlib.GetLastError();
-                    string msg = Mono.Unix.UnixMarshal.GetErrorDescription(errno);
-                    int error = Mono.Unix.Native.NativeConvert.FromErrno(errno);
-                    throw PythonOps.OSError(error, msg);
+                    throw PythonNT.GetLastUnixError();
                 }
 
                 return size;

Src/IronPython.Modules/nt.cs

@@ -2313,7 +2313,7 @@ private static Exception DirectoryExistsError(string? filename) {
         }
 
 
-        private static Exception GetOsError(int error, string? filename = null, string? filename2 = null)
+        internal static Exception GetOsError(int error, string? filename = null, string? filename2 = null)
             => PythonOps.OSError(error, strerror(error), filename, null, filename2);
 
 #if FEATURE_NATIVE || FEATURE_CTYPES

Src/IronPython.Modules/posix.cs

@@ -28,7 +28,7 @@ public static partial class PythonNT {
 
         [SupportedOSPlatform("linux")]
         [SupportedOSPlatform("osx")]
-        private static Exception GetLastUnixError(string? filename = null, string? filename2 = null)
+        internal static Exception GetLastUnixError(string? filename = null, string? filename2 = null)
             // On POSIX, GetLastWin32Error returns the errno value, same as GetLastPInvokeError
             => GetOsError(Marshal.GetLastWin32Error(), filename, filename2);