Fix progress bar since Windows doesn't support ANSI escape codes

* Use the colorama module to enable the "clear the line" ANSI escape
  code on Windows.
* Disable cursor hiding on Windows since Windows terminal doesn't
  support it nor does colorama.

pip/utils/ui.py

@@ -4,12 +4,20 @@ from __future__ import division
 import itertools
 import sys
 
+from pip.compat import WINDOWS
 from pip.utils import format_size
 from pip.utils.logging import get_indentation
 from pip._vendor.progress.bar import Bar
 from pip._vendor.progress.helpers import WritelnMixin
 from pip._vendor.progress.spinner import Spinner
 
+try:
+    from pip._vendor import colorama
+# Lots of different errors can come from this, including SystemError and
+# ImportError.
+except Exception:
+    colorama = None
+
 
 class DownloadProgressMixin(object):
 
@@ -41,14 +49,40 @@ class DownloadProgressMixin(object):
         self.finish()
 
 
-class DownloadProgressBar(DownloadProgressMixin, Bar):
+class WindowsMixin(object):
+
+    def __init__(self, *args, **kwargs):
+        super(WindowsMixin, self).__init__(*args, **kwargs)
+
+        # Check if we are running on Windows and we have the colorama module,
+        # if we do then wrap our file with it.
+        if WINDOWS and colorama:
+            self.file = colorama.AnsiToWin32(self.file)
+            # The progress code expects to be able to call self.file.isatty()
+            # but the colorama.AnsiToWin32() object doesn't have that, so we'll
+            # add it.
+            self.file.isatty = lambda: self.file.wrapped.isatty()
+            # The progress code expects to be able to call self.file.flush()
+            # but the colorama.AnsiToWin32() object doesn't have that, so we'll
+            # add it.
+            self.file.flush = lambda: self.file.wrapped.flush()
+
+        # The Windows terminal does not support the hide/show cursor ANSI codes
+        # even with colorama. So we'll ensure that hide_cursor is False on
+        # Windows.
+        if WINDOWS and self.hide_cursor:
+            self.hide_cursor = False
+
+
+class DownloadProgressBar(WindowsMixin, DownloadProgressMixin, Bar):
 
     file = sys.stdout
     message = "%(percent)d%%"
     suffix = "%(downloaded)s %(download_speed)s %(pretty_eta)s"
 
 
-class DownloadProgressSpinner(DownloadProgressMixin, WritelnMixin, Spinner):
+class DownloadProgressSpinner(WindowsMixin, DownloadProgressMixin,
+                              WritelnMixin, Spinner):
 
     file = sys.stdout
     suffix = "%(downloaded)s %(download_speed)s"