Make test_socket work.

Don't exclude test_socket from the tests to run.

Lib/io.py

@@ -300,17 +300,23 @@ class IOBase:
 
     def readline(self, limit: int = -1) -> bytes:
         """For backwards compatibility, a (slowish) readline()."""
-        if limit is None:
-            limit = -1
-        res = bytes()
-        while limit < 0 or len(res) < limit:
+        if hasattr(self, "peek"):
+            def nreadahead():
                 readahead = self.peek(1, unsafe=True)
                 if not readahead:
-                break
+                    return 1
                 n = (readahead.find(b"\n") + 1) or len(readahead)
                 if limit >= 0:
                     n = min(n, limit)
-            b = self.read(n)
+                return n
+        else:
+            def nreadahead():
+                return 1
+        if limit is None:
+            limit = -1
+        res = bytes()
+        while limit < 0 or len(res) < limit:
+            b = self.read(nreadahead())
             if not b:
                 break
             res += b

runtests.sh

@@ -27,7 +27,7 @@ mkdir -p OUT
 # Compute the list of tests to run.
 case $# in
 0) 
-    TESTS=`(cd Lib/test; ls test_*.py | sed 's/\.py//' | grep -v  test_socket)`
+    TESTS=`(cd Lib/test; ls test_*.py | sed 's/\.py//')`
     ;;
 *)
     TESTS="$@"