do not anyhow change text pasted to a string literal

fixed PY-9566 pasting code on an indented line inserts that indentation at the end of the line

python/src/com/jetbrains/python/editor/PythonCopyPasteProcessor.java

@@ -61,6 +61,9 @@ public class PythonCopyPasteProcessor implements CopyPastePreProcessor {
     final int lineNumber = document.getLineNumber(caretOffset);
     final int lineStartOffset = getLineStartSafeOffset(document, lineNumber);
 
+    final PsiElement element = file.findElementAt(caretOffset);
+    if (PsiTreeUtil.getParentOfType(element, PyStringLiteralExpression.class) != null) return text;
+
     text = addLeadingSpaces(text, NOT_INDENT_FILTER, indentSize, indentChar);
     int firstLineIndent = StringUtil.findFirst(text, NOT_INDENT_FILTER);
     final String indentText = getIndentText(file, document, caretOffset, lineNumber, firstLineIndent);

python/testData/copyPaste/PasteToStringLiteral.after.py

@@ -0,0 +1,3 @@
+if True:
+    s = "foo"
+    'foo'

python/testData/copyPaste/PasteToStringLiteral.dst.py

@@ -0,0 +1,3 @@
+if True:
+    s = "foo"
+    '<caret>'

python/testData/copyPaste/PasteToStringLiteral.src.py

@@ -0,0 +1,2 @@
+if True:
+    s = "<selection>foo</selection>"

python/testSrc/com/jetbrains/python/PyCopyPasteTest.java

@@ -309,6 +309,10 @@ public class PyCopyPasteTest extends PyTestCase {
     doTest();
   }
 
+  public void testPasteToStringLiteral() {
+    doTest();
+  }
+
   private void doTestTabs() {
     final CommonCodeStyleSettings.IndentOptions indentOptions =
       CodeStyleSettingsManager.getSettings(myFixture.getProject()).getIndentOptions(PythonFileType.INSTANCE);