Fix #162: Make pure Python quoter consistent with Cython version

tests/test_quoting.py

@@ -345,3 +345,8 @@ def test_quote_very_large_string(quoter):
     # more than 8 KiB
     s = 'abcфух%30%0a' * 1024
     assert quoter()(s) == 'abc%D1%84%D1%83%D1%850%0A' * 1024
+
+
+def test_space(quoter):
+    s = '% A'
+    assert quoter()(s) == '%25%20A'

yarl/quoting.py

@@ -1,3 +1,4 @@
+import re
 from string import ascii_letters, ascii_lowercase, digits
 
 BASCII_LOWERCASE = ascii_lowercase.encode('ascii')
@@ -10,6 +11,9 @@
 ALLOWED = UNRESERVED + SUB_DELIMS_WITHOUT_QS
 
 
+_IS_HEX = re.compile(b'[A-Z0-9][A-Z0-9]')
+
+
 class _PyQuoter:
     def __init__(self, *, safe='', protected='', qs=False):
         self._safe = safe
@@ -39,10 +43,16 @@ def __call__(self, val):
 
             if pct:
                 if ch in BASCII_LOWERCASE:
-                    ch = ch - 32
+                    ch = ch - 32  # convert to uppercase
                 pct.append(ch)
                 if len(pct) == 3:  # pragma: no branch   # peephole optimizer
                     pct = bytes(pct)
+                    buf = pct[1:]
+                    if not _IS_HEX.match(buf):
+                        ret.extend(b'%25')
+                        pct = b''
+                        idx -= 2
+                        continue
                     try:
                         unquoted = chr(int(pct[1:].decode('ascii'), base=16))
                     except ValueError: