Fix generated Python code for Doxygen comments with triple quotes

In addition to the changes in the previous commit, also avoid syntax
errors in the generated Python docstrings by splitting them into several
parts if there are 3 quotes in a row in the input, as it's impossible to
have them inside triple-quoted strings, generally speaking (i.e. if
there are occurrences of both """ and ''' inside the string).

Source/Modules/python.cxx

@@ -1599,6 +1599,16 @@ public:
 
     Append(doc, useSingleQuotes ? "r'''" : "r\"\"\"");
 
+    // We also need to avoid having triple quotes of whichever type we use, as
+    // this would break Python doc string syntax too. Unfortunately there is no
+    // way to have triple quotes inside of raw-triple-quoted string, so we have
+    // to break the string in parts and rely on concatenation of the adjacent
+    // string literals.
+    if (useSingleQuotes)
+      Replaceall(docstr, "'''", "''' \"'''\" '''");
+    else
+      Replaceall(docstr, "\"\"\"", "\"\"\" '\"\"\"' \"\"\"");
+
     Append(doc, docstr);
     Append(doc, useSingleQuotes ? "'''" : "\"\"\"");
     Delete(docstr);