Fix #5294: sphinx-quickstart blank prompts in PowerShell

CHANGES

@@ -32,6 +32,7 @@ Bugs fixed
 * #5211: autodoc: No docs generated for functools.partial functions
 * #5306: autodoc: ``getargspec()`` raises NameError for invalid typehints
 * #5298: imgmath: math_number_all causes equations to have two numbers in html
+* #5294: sphinx-quickstart blank prompts in PowerShell
 
 Testing
 --------

sphinx/cmd/quickstart.py

@@ -78,6 +78,12 @@ DEFAULTS = {
 
 PROMPT_PREFIX = '> '
 
+if sys.platform == 'win32':
+    # On Windows, show questions as bold because of color scheme of PowerShell (refs: #5294).
+    COLOR_QUESTION = 'bold'
+else:
+    COLOR_QUESTION = 'purple'
+
 
 # function to get input from terminal -- overridden by the test suite
 def term_input(prompt):
@@ -189,7 +195,7 @@ def do_prompt(text, default=None, validator=nonempty):
                         prompt = prompt.encode('utf-8')
                     except UnicodeEncodeError:
                         prompt = prompt.encode('latin1')
-        prompt = colorize('purple', prompt, input_mode=True)
+        prompt = colorize(COLOR_QUESTION, prompt, input_mode=True)
         x = term_input(prompt).strip()
         if default and not x:
             x = default