better recovery for syntax errors in parameter list (PY-3635); fix old bug with tuple parameters parsing

python/testData/psi/ErrorInParameterList.py

@@ -0,0 +1,2 @@
+def select2 (self,filds=None, from=''):
+        print (sql)

python/testData/psi/ErrorInParameterList.txt

@@ -0,0 +1,34 @@
+PyFile:ErrorInParameterList.py
+  PyFunction('select2')
+    PsiElement(Py:DEF_KEYWORD)('def')
+    PsiWhiteSpace(' ')
+    PsiElement(Py:IDENTIFIER)('select2')
+    PsiWhiteSpace(' ')
+    PyParameterList
+      PsiElement(Py:LPAR)('(')
+      PyNamedParameter('self')
+        PsiElement(Py:IDENTIFIER)('self')
+      PsiElement(Py:COMMA)(',')
+      PyNamedParameter('filds')
+        PsiElement(Py:IDENTIFIER)('filds')
+        PsiElement(Py:EQ)('=')
+        PyReferenceExpression: None
+          PsiElement(Py:IDENTIFIER)('None')
+      PsiElement(Py:COMMA)(',')
+      PsiWhiteSpace(' ')
+      PsiErrorElement:formal parameter name expected
+        PsiElement(Py:FROM_KEYWORD)('from')
+        PsiElement(Py:EQ)('=')
+        PsiElement(Py:STRING_LITERAL)('''')
+      PsiElement(Py:RPAR)(')')
+    PsiElement(Py:COLON)(':')
+    PsiWhiteSpace('\n        ')
+    PyStatementList
+      PyPrintStatement
+        PsiElement(Py:PRINT_KEYWORD)('print')
+        PsiWhiteSpace(' ')
+        PyParenthesizedExpression
+          PsiElement(Py:LPAR)('(')
+          PyReferenceExpression: sql
+            PsiElement(Py:IDENTIFIER)('sql')
+          PsiElement(Py:RPAR)(')')