diff --git a/Lib/_codecs.py b/Lib/_codecs.py
index 807218687..f9b8f17b8 100644
--- a/Lib/_codecs.py
+++ b/Lib/_codecs.py
@@ -1610,8 +1610,8 @@ def PyUnicode_DecodeRawUnicodeEscape(s, size, errors):
     while (pos < len(s)):
         ch = s[pos]
     #/* Non-escape characters are interpreted as Unicode ordinals */
-        if (ch != '\\'):
-            p += chr(ord(ch))
+        if (ch != ord('\\')):
+            p.append(chr(ch))
             pos += 1
             continue        
         startinpos = pos
@@ -1619,20 +1619,20 @@ def PyUnicode_DecodeRawUnicodeEscape(s, size, errors):
 ##         backslashes is odd */
         bs = pos
         while pos < size:
-            if (s[pos] != '\\'):
+            if (s[pos] != ord('\\')):
                 break
-            p += chr(ord(s[pos]))
+            p.append(chr(s[pos]))
             pos += 1
     
         if (((pos - bs) & 1) == 0 or
             pos >= size or
-            (s[pos] != 'u' and s[pos] != 'U')) :
-            p += chr(ord(s[pos]))
+            (s[pos] != ord('u') and s[pos] != ord('U'))) :
+            p.append(chr(s[pos]))
             pos += 1
             continue
         
         p.pop(-1)
-        if s[pos] == 'u':
+        if s[pos] == ord('u'):
             count = 4 
         else: 
             count = 8
@@ -1646,7 +1646,7 @@ def PyUnicode_DecodeRawUnicodeEscape(s, size, errors):
             res = unicode_call_errorhandler(
                     errors, "rawunicodeescape", "truncated \\uXXXX",
                     s, size, pos, pos+count)
-            p += res[0]
+            p.append(res[0])
             pos = res[1]
         else:
     #ifndef Py_UNICODE_WIDE
@@ -1656,9 +1656,9 @@ def PyUnicode_DecodeRawUnicodeEscape(s, size, errors):
                         errors, "rawunicodeescape", "\\Uxxxxxxxx out of range",
                         s, size, pos, pos+1)
                     pos = res[1]
-                    p += res[0]
+                    p.append(res[0])
                 else:
-                    p += chr(x)
+                    p.append(chr(x))
                     pos += count
             else:
                 if (x > 0x10000):
@@ -1666,11 +1666,11 @@ def PyUnicode_DecodeRawUnicodeEscape(s, size, errors):
                         errors, "rawunicodeescape", "\\Uxxxxxxxx out of range",
                         s, size, pos, pos+1)
                     pos = res[1]
-                    p += res[0]
+                    p.append(res[0])
 
     #endif
                 else:
-                    p += chr(x)
+                    p.append(chr(x))
                     pos += count
 
     return p
diff --git a/Lib/pickle.py b/Lib/pickle.py
index c8370c9f7..7ba419394 100644
--- a/Lib/pickle.py
+++ b/Lib/pickle.py
@@ -201,7 +201,10 @@ class _Framer:
         if self.current_frame:
             f = self.current_frame
             if f.tell() >= self._FRAME_SIZE_TARGET or force:
-                with f.getbuffer() as data:
+                # XXX RUSTPYTHON TODO: memoryview + BytesIO.getbuffer()
+                # with f.getbuffer() as data:
+                data = f.getvalue()
+                if True:
                     n = len(data)
                     write = self.file_write
                     write(FRAME)
diff --git a/compiler/src/compile.rs b/compiler/src/compile.rs
index 26eca75a4..a3b758443 100644
--- a/compiler/src/compile.rs
+++ b/compiler/src/compile.rs
@@ -479,7 +479,9 @@ impl<O: OutputStream> Compiler<O> {
 
                 self.compile_statements(body)?;
 
-                for end_label in end_labels {
+                // sort of "stack up" the layers of with blocks:
+                // with a, b: body -> start_with(a) start_with(b) body() end_with(b) end_with(a)
+                for end_label in end_labels.into_iter().rev() {
                     self.emit(Instruction::PopBlock);
                     self.emit(Instruction::EnterFinally);
                     self.set_label(end_label);
diff --git a/parser/src/fstring.rs b/parser/src/fstring.rs
index 4540c005d..7af0cb404 100644
--- a/parser/src/fstring.rs
+++ b/parser/src/fstring.rs
@@ -81,8 +81,7 @@ impl<'a> FStringParser<'a> {
 
                 // match a python 3.8 self documenting expression
                 // format '{' PYTHON_EXPRESSION '=' FORMAT_SPECIFIER? '}'
-                '=' if self.chars.peek() != Some(&'=') => {
-                    // check for delims empty?
+                '=' if self.chars.peek() != Some(&'=') && delims.is_empty() => {
                     pred_expression_text = expression.to_string(); // safe expression before = to print it
                 }
 
diff --git a/src/main.rs b/src/main.rs
index 55a7ef724..80639aae6 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -169,6 +169,12 @@ fn parse_arguments<'a>(app: App<'a, '_>) -> ArgMatches<'a> {
                 .short("X")
                 .takes_value(true)
                 .help("set implementation-specific option"),
+        )
+        .arg(
+            Arg::with_name("warning-control")
+                .short("W")
+                .takes_value(true)
+                .help("warning control; arg is action:message:category:module:lineno"),
         );
     #[cfg(feature = "flame-it")]
     let app = app
diff --git a/vm/src/obj/objtype.rs b/vm/src/obj/objtype.rs
index 39c752675..5bcabb47b 100644
--- a/vm/src/obj/objtype.rs
+++ b/vm/src/obj/objtype.rs
@@ -171,7 +171,10 @@ impl PyClassRef {
                 ],
             )
         } else {
-            Err(vm.new_attribute_error(format!("{} has no attribute '{}'", self, name)))
+            Err(vm.new_attribute_error(format!(
+                "type object '{}' has no attribute '{}'",
+                self, name
+            )))
         }
     }
 
diff --git a/vm/src/stdlib/io.rs b/vm/src/stdlib/io.rs
index 9363f5bae..7f4c53e9f 100644
--- a/vm/src/stdlib/io.rs
+++ b/vm/src/stdlib/io.rs
@@ -1324,6 +1324,7 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
 
     //StringIO: in-memory text
     let string_io = py_class!(ctx, "StringIO", text_io_base.clone(), {
+        "__module__" => ctx.new_str("_io"),
         (slot new) => string_io_new,
         "seek" => ctx.new_method(PyStringIORef::seek),
         "seekable" => ctx.new_method(PyStringIORef::seekable),