[7.1.0] Fix up permissions error in getInputStream, like we already do for getOutputStream.

src/main/java/com/google/devtools/build/lib/vfs/AbstractFileSystem.java

@@ -61,6 +61,12 @@ protected InputStream getInputStream(PathFragment path) throws IOException {
         if (e.getMessage().endsWith("(Interrupted system call)")) {
           continue;
         } else {
+          // FileInputStream throws FileNotFoundException if opening fails for any reason,
+          // including permissions. Fix it up here.
+          // TODO(tjgq): Migrate to java.nio.
+          if (e.getMessage().equals(path + ERR_PERMISSION_DENIED)) {
+            throw new FileAccessException(e.getMessage());
+          }
           throw e;
         }
       }
@@ -158,9 +164,9 @@ protected OutputStream getOutputStream(PathFragment path, boolean append, boolea
     try {
       return createFileOutputStream(path, append, internal);
     } catch (FileNotFoundException e) {
-      // Why does it throw a *FileNotFoundException* if it can't write?
-      // That does not make any sense! And its in a completely different
-      // format than in other situations, no less!
+      // FileOutputStream throws FileNotFoundException if opening fails for any reason,
+      // including permissions. Fix it up here.
+      // TODO(tjgq): Migrate to java.nio.
       if (e.getMessage().equals(path + ERR_PERMISSION_DENIED)) {
         throw new FileAccessException(e.getMessage());
       }

src/test/java/com/google/devtools/build/lib/vfs/FileSystemTest.java

@@ -1304,6 +1304,20 @@ public void testInputAndOutputStream() throws Exception {
     }
   }
 
+  @Test
+  public void testInputStreamPermissionError() throws Exception {
+    assertThat(xFile.exists()).isTrue();
+    xFile.setReadable(false);
+    assertThrows(FileAccessException.class, () -> xFile.getInputStream());
+  }
+
+  @Test
+  public void testOutputStreamPermissionError() throws Exception {
+    assertThat(xFile.exists()).isTrue();
+    xFile.setWritable(false);
+    assertThrows(FileAccessException.class, () -> xFile.getOutputStream());
+  }
+
   @Test
   public void testFileChannel() throws Exception {
     byte[] bytes = "abcdefghijklmnoprstuvwxyz".getBytes(StandardCharsets.ISO_8859_1);