Add two more issues one about strings and one about an import.

parso/python/normalizer.py

@@ -8,6 +8,10 @@ _STAR_EXPR_PARENTS = ('testlist_star_expr', 'testlist_comp', 'exprlist')
 _MAX_BLOCK_SIZE = 20
 
 
+def _is_bytes_literal(string):
+    return 'b' in string.string_prefix.lower()
+
+
 def _iter_stmts(scope):
     """
     Iterates over all statements and splits up  simple_stmt.
@@ -123,6 +127,11 @@ class ErrorFinder(Normalizer):
                 and _is_future_import(node) and not _is_future_import_first(node):
             message = "from __future__ imports must occur at the beginning of the file"
             self._add_syntax_error(message, node)
+        elif node.type == 'import_as_names':
+            if node.children[-1] == ',':
+                # from foo import a,
+                message = "trailing comma not allowed without surrounding parentheses"
+                self._add_syntax_error(message, node)
         elif node.type in _STAR_EXPR_PARENTS:
             if node.parent.type == 'del_stmt':
                 self._add_syntax_error("can't use starred expression here", node.parent)
@@ -153,6 +162,17 @@ class ErrorFinder(Normalizer):
                 # foo(x for x in [], b)
                 message = "Generator expression must be parenthesized if not sole argument"
                 self._add_syntax_error(message, node)
+        elif node.type == 'atom':
+            first = node.children[0]
+            # e.g. 's' b''
+            message = "cannot mix bytes and nonbytes literals"
+            # TODO this check is only relevant for Python 3+
+            if first.type == 'string':
+                first_is_bytes = _is_bytes_literal(first)
+                for string in node.children[1:]:
+                    if first_is_bytes != _is_bytes_literal(string):
+                        self._add_syntax_error(message, node)
+                        break
 
         yield
 

parso/python/tree.py

@@ -25,6 +25,8 @@ Any subclasses of :class:`Scope`, including :class:`Module` has an attribute
 [<ImportName: import os@1,0>]
 """
 
+import re
+
 from parso._compatibility import utf8_repr, unicode
 from parso.tree import Node, BaseNode, Leaf, ErrorNode, ErrorLeaf, \
     search_ancestor
@@ -208,6 +210,10 @@ class String(Literal):
     type = 'string'
     __slots__ = ()
 
+    @property
+    def string_prefix(self):
+        return re.match('\w*(?=[\'"])', self.value).group(0)
+
 
 class _StringComparisonMixin(object):
     def __eq__(self, other):

test/normalizer_issue_files/allowed_syntax.py

@@ -5,6 +5,10 @@ gather some of the potentially dangerous ones.
 
 from __future__ import division
 
+'' ''
+''r''u''
+b'' BR''
+
 for x in [1]:
     try:
         continue  # Only the other continue and pass is an error.

test/test_python_errors.py

@@ -72,6 +72,7 @@ def test_indentation_errors(code, positions):
         'yield',
         'try: pass\nexcept: pass\nexcept X: pass',
         'f(x for x in bar, 1)',
+        'from foo import a,',
 
         # IndentationError
         ' foo',
@@ -111,6 +112,7 @@ def test_python_exception_matches(code):
         ('async def foo():\n def nofoo():[x async for x in []]', '3.6'),
         ('[*[] for a in [1]]', '3.5'),
         ('{**{} for a in [1]}', '3.5'),
+        ('"s" b""', '3.5'),
     ]
 )
 def test_python_exception_matches_version(code, version):