Python: Add a test for handling of corner-case strings.

python/ql/test/library-tests/exprs/strings/Strings.expected

@@ -0,0 +1,4 @@
+| test.py:3:1:3:33 | test.py:3 | u' | [\ufffd-\ufffd][\ufffd-\ufffd] |
+| test.py:5:1:5:26 | test.py:5 | u' | [\ufffd-\ufffd] |
+| test.py:8:1:8:20 | test.py:8 | u' | {}\r{}{:<{width}} |
+| test.py:9:1:9:15 | test.py:9 | u' | {}\r{}{:<{}} |

python/ql/test/library-tests/exprs/strings/Strings.ql

@@ -0,0 +1,5 @@
+
+import python
+
+from StrConst s
+select s.getLocation(), s.getPrefix(), s.getText()

python/ql/test/library-tests/exprs/strings/test.py

@@ -0,0 +1,9 @@
+
+#Half Surrogate pairs
+u'[\uD800-\uDBFF][\uDC00-\uDFFF]'
+#Outside BMP
+u'[\U00010000-\U0010ffff]'
+
+#Troublesome format strings
+u'{}\r{}{:<{width}}'
+u'{}\r{}{:<{}}'