Merge branch 'str_replace_regex' of https://github.com/Liam3851/pandas

into str_replace_regex

# Conflicts:
#	doc/source/whatsnew/v0.23.0.txt
#	pandas/core/strings.py

doc/source/whatsnew/v0.23.0.txt

@@ -620,6 +620,7 @@ Other API Changes
 - Set operations (union, difference...) on :class:`IntervalIndex` with incompatible index types will now raise a ``TypeError`` rather than a ``ValueError`` (:issue:`19329`)
 - :class:`DateOffset` objects render more simply, e.g. ``<DateOffset: days=1>`` instead of ``<DateOffset: kwds={'days': 1}>`` (:issue:`19403`)
 - ``Categorical.fillna`` now validates its ``value`` and ``method`` keyword arguments. It now raises when both or none are specified, matching the behavior of :meth:`Series.fillna` (:issue:`19682`)
+- :func:`pandas.merge` provides a more informative error message when trying to merge on timezone-aware and timezone-naive columns (:issue:`15800`)
 - :func:`Series.str.replace` now takes an optional `regex` keyword which, when set to ``False``, uses literal string replacement rather than regex replacement (:issue:`16808`) 
 
 .. _whatsnew_0230.deprecations:

pandas/core/strings.py

@@ -376,6 +376,16 @@ def str_replace(arr, pat, repl, n=-1, case=None, flags=0, regex=True):
     2    NaN
     dtype: object
 
+    When `pat` is a string and `regex` is True, the given `pat` is compiled
+    as a regex. When `repl` is a string, it replaces matching regex patterns
+    as with :meth:`re.sub`:
+
+    >>> pd.Series(['foo', 'fuz', np.nan]).str.replace('f.', 'ba', regex=True)
+    0    bao
+    1    baz
+    2    NaN
+    dtype: object
+
     When `repl` is a callable, it is called on every `pat` using
     :func:`re.sub`. The callable should expect one positional argument
     (a regex object) and return a string.