remove magic-specific empty cell warnings

IPython/core/magics/execution.py

@@ -776,9 +776,6 b' python-profiler package from non-free.""")'
                                         posix=False, strict=False)
         if stmt == "" and cell is None:
             return
-        elif cell == '':
-            warn("Empty cell. Did you mean to use %timeit?")
-            return
         
         timefunc = timeit.default_timer
         number = int(getattr(opts, "n", 0))

IPython/core/magics/osm.py

@@ -36,7 +36,7 b' from IPython.utils.openpy import source_to_unicode'
 from IPython.utils.path import get_py_filename, unquote_filename
 from IPython.utils.process import abbrev_cwd
 from IPython.utils.terminal import set_term_title
-from IPython.utils.warn import warn
+
 #-----------------------------------------------------------------------------
 # Magic implementation classes
 #-----------------------------------------------------------------------------
@@ -595,9 +595,6 b' class OSMagics(Magics):'
         if cell is None:
             # line magic
             return self.shell.getoutput(line)
-        elif cell == '':
-            warn("Empty cell. Did you mean to use %!, %sx, or %system?")
-            return
         else:
             opts,args = self.parse_options(line, '', 'out=')
             output = self.shell.getoutput(cell)