Rollbacked support for empty strings in powershell as it doesn't pass on

the CI.

README.md

@@ -14,7 +14,9 @@ Also, while this library is in Python, it aims to be a reference implementation
 
 ## Known limitations
 
-* ASCII control codes are not supported. This notably includes `\t`, `\r` and `\n`. (There doest't seem to have proper ways to encode these characters in CMD nor Powershell anyway.)
+* Some common control characters like `\t` and `\n` are supported in Powershell. Other control characters are not.
+* No control characters are supported at all in CMD, including `\t` and `\n`. (There doest't seem to have proper ways to encode these characters in CMD.)
+* Empty strings are not supported in Powershell. (It doesn't seem to be possible at all to pass an empty string in all versions of Powershell.)
 
 ## About non-ASCII characters
 

test_win_cmd_escaper.py

@@ -21,9 +21,6 @@ def test_basic_calls(self):
         self._test_str("hello")
         self._test_str("hello world")
 
-    def test_empty(self):
-        self._test_str("")
-
     def test_printable_ascii_only_char(self):
         for i in range(32, 127):
             character = chr(i)
@@ -129,6 +126,9 @@ def test_backticks(self):
 
 class AllCmdTests(AllTests):
 
+    def test_empty(self):
+        self._test_str("")
+
     def test_other_control_characters(self):
         for c in powershell_supported_control_characters:
             self._test_unsupported(c)
@@ -158,6 +158,9 @@ def escape(self, str):
     def run_echoer(self, str):
         return test_utils.run_echoer_with_powershell_through_script(str)
 
+    def test_empty(self):
+        self._test_unsupported("")
+
     def test_other_control_characters(self):
         for c in powershell_supported_control_characters:
             self._test_str(c)

win_cmd_escaper.py

@@ -50,6 +50,8 @@ def escape_powershell_argument_script(str):
     """
     Escapes an argument for Powershell.
     """
+    if str == "":
+        raise ValueError("Empty strings are not supported")
 
     acc = ""
     for i in range(len(str)):