tests: fix readline escape characters in heredoctest.py/test-url.py

This fix mirrors the changes made to test-doctest.py in b856071435f7
and 967adcf5910d.

Without this change, tests running heredoctest.py can fail on certain
versions of OS X when TERM is set to xterm-256color:

   $ /opt/local/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python -m heredoctest <<EOF
   > >>> open('b', 'w').write('this' * 1000)
   > EOF
+  \x1b[?1034h (no-eol) (esc)

A similar problem occurs with test-url.py:

  $ ./run-tests.py test-url.py

  --- .../tests/test-url.py.out
  +++ .../tests/test-url.py.err
  @@ -0,0 +1 @@
  +
  ERROR: .../test-url.py output changed
  !
  Failed test-url.py: output changed
  # Ran 1 tests, 0 skipped, 1 failed.

tests/heredoctest.py

@@ -1,6 +1,9
 import doctest, tempfile, os, sys
 
 if __name__ == "__main__":
+    if 'TERM' in os.environ:
+        del os.environ['TERM']
+
     fd, name = tempfile.mkstemp(suffix='hg-tst')
 
     try:

tests/test-url.py

@@ -1,4 +1,4
-import sys
+import os
 
 def check(a, b):
     if a != b:
@@ -232,4 +232,7 def test_url():
     'foo/bar/baz'
     """
 
+if 'TERM' in os.environ:
+    del os.environ['TERM']
+
 doctest.testmod(optionflags=doctest.NORMALIZE_WHITESPACE)