Replaced clipboard copy and paste custom code with pyperclip

- Added a 3rd-party dependency on the pyperclip module

TODO: Rigorous test on all OSes, particularly Linux systems without xclip

7 files changed, 33 insertions, 142 deletions

diff --git a/CHANGES.md b/CHANGES.md
index d84e6b74..b853f222 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -17,7 +17,9 @@ News
     * Removed presence of a default file name and default file extension
         * These also strongly felt out of place
         * ``load`` and ``_relative_load`` now require a file path
-        * ``edit`` and ``save`` now use a temporary file if a file path isn't provided   
+        * ``edit`` and ``save`` now use a temporary file if a file path isn't provided
+    * Load command has better error checking and reporting
+    * Clipboard copy and paste functionality is now handled by the ``pyperclip`` module
     
 0.7.3
 -----
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index a0a6b21e..ffac39bf 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -42,11 +42,12 @@ The tables below list all prerequisites along with the minimum required version
 
 #### Prerequisites to run cmd2 applications
 
-| Prerequisite                                | Minimum Version |
-| ------------------------------------------- | --------------- |
-| [Python](https://www.python.org/downloads/) | `3.3 or 2.7`    |
-| [six](https://pypi.python.org/pypi/six)     | `1.8`           |
-| [pyparsing](http://pyparsing.wikispaces.com)| `2.0.3`         |
+| Prerequisite                                        | Minimum Version |
+| --------------------------------------------------- | --------------- |
+| [Python](https://www.python.org/downloads/)         | `3.3 or 2.7`    |
+| [six](https://pypi.python.org/pypi/six)             | `1.8`           |
+| [pyparsing](http://pyparsing.wikispaces.com)        | `2.0.3`         |
+| [pyperclip](https://github.com/asweigart/pyperclip) | `1.5`           |
 
 #### Additional prerequisites to run cmd2 unit tests
 
diff --git a/README.md b/README.md
index 862622f3..1642b4b5 100755
--- a/README.md
+++ b/README.md
@@ -9,7 +9,8 @@ cmd2
 
 cmd2 is a tool for writing command-line interactive applications for Python 2.7 and Python 3.3+.  It is based on the
 Python Standard Library's [cmd](https://docs.python.org/3/library/cmd.html) module, and can be used any place cmd is used simply by importing cmd2 instead.  It is
-pure Python code with the only 3rd-party dependencies being on [six](https://pypi.python.org/pypi/six) and [pyparsing](http://pyparsing.wikispaces.com).
+pure Python code with the only 3rd-party dependencies being on [six](https://pypi.python.org/pypi/six), [pyparsing](http://pyparsing.wikispaces.com),
+and [pyperclip](https://github.com/asweigart/pyperclip).
 
 The latest documentation for cmd2 can be read online here: https://cmd2.readthedocs.io/en/latest/
 
diff --git a/cmd2.py b/cmd2.py
index f54a8555..cf98ba05 100755
--- a/cmd2.py
+++ b/cmd2.py
@@ -44,6 +44,7 @@ from code import InteractiveConsole
 from optparse import make_option
 
 import pyparsing
+import pyperclip
 
 # next(it) gets next item of iterator it. This is a replacement for calling it.next() in Python 2 and next(it) in Py3
 from six import next
@@ -301,148 +302,32 @@ def options(option_list, arg_desc="arg"):
     return option_setup
 
 
-# Prefix to use on all OSes when the appropriate library or CLI tool isn't installed for getting access to paste buffer
-pastebufferr = """Redirecting to or from paste buffer requires %s
-to be installed on operating system.
-%s"""
-
 # Can we access the clipboard?
-can_clip = False
-if sys.platform == "win32":
-    # Running on Windows
-    try:
-        # noinspection PyUnresolvedReferences
-        import win32clipboard
-
-        def get_paste_buffer():
-            """Get the contents of the clipboard for Windows OSes.
+can_clip = True
 
-            :return: str - contents of the clipboard
-            """
-            win32clipboard.OpenClipboard(0)
-            try:
-                result = win32clipboard.GetClipboardData()
-            except TypeError:
-                result = ''  # non-text
-            win32clipboard.CloseClipboard()
-            return result
 
-        def write_to_paste_buffer(txt):
-            """Paste text to the clipboard for Windows OSes.
-
-            :param txt: str - text to paste to the clipboard
-            """
-            win32clipboard.OpenClipboard(0)
-            win32clipboard.EmptyClipboard()
-            win32clipboard.SetClipboardText(txt)
-            win32clipboard.CloseClipboard()
-
-        can_clip = True
-    except ImportError:
-        # noinspection PyUnusedLocal
-        def get_paste_buffer(*args):
-            """For Windows OSes without the appropriate library installed to get text from clipboard, raise an exception.
-            """
-            raise OSError(pastebufferr % ('pywin32', 'Download from http://sourceforge.net/projects/pywin32/'))
-
-        write_to_paste_buffer = get_paste_buffer
-elif sys.platform == 'darwin':
-    # Running on Mac OS X
-    try:
-        # Warning: subprocess.call() and subprocess.check_call() should never be called with stdout=PIPE or stderr=PIPE
-        # because the child process will block if it generates enough output to a pipe to fill up the OS pipe buffer.
-        # Starting with Python 3.5 there is a newer, safer API based on the run() function.
-
-        # Python 3.3+ supports subprocess.DEVNULL, but that isn't defined for Python 2.7
-        with open(os.devnull, 'w') as DEVNULL:
-            # test for pbcopy - AFAIK, should always be installed on MacOS
-            subprocess.check_call(['pbcopy', '-help'], stdin=subprocess.PIPE, stdout=DEVNULL, stderr=DEVNULL)
-        can_clip = True
-    except (subprocess.CalledProcessError, OSError, IOError):
-        pass
-    if can_clip:
-        def get_paste_buffer():
-            """Get the contents of the clipboard for Mac OS X.
-
-            :return: str - contents of the clipboard
-            """
-            pbcopyproc = subprocess.Popen('pbpaste', stdin=subprocess.PIPE, stdout=subprocess.PIPE,
-                                          stderr=subprocess.PIPE)
-            stdout, stderr = pbcopyproc.communicate()
-            if six.PY3:
-                return stdout.decode()
-            else:
-                return stdout
+def get_paste_buffer():
+    """Get the contents of the clipboard / paste buffer.
 
-        def write_to_paste_buffer(txt):
-            """Paste text to the clipboard for Mac OS X.
+    :return: str - contents of the clipboard
+    """
+    pb_unicode = pyperclip.paste()
 
-            :param txt: str - text to paste to the clipboard
-            """
-            pbcopyproc = subprocess.Popen('pbcopy', stdin=subprocess.PIPE, stdout=subprocess.PIPE,
-                                          stderr=subprocess.PIPE)
-            if six.PY3:
-                pbcopyproc.communicate(txt.encode())
-            else:
-                pbcopyproc.communicate(txt)
+    if six.PY3:
+        pb_str = pb_unicode
     else:
-        # noinspection PyUnusedLocal
-        def get_paste_buffer(*args):
-            """For Mac OS X without the appropriate tool installed to get text from clipboard, raise an exception."""
-            raise OSError(pastebufferr % ('pbcopy',
-                                          'On MacOS X - error should not occur - part of the default installation'))
-
-        write_to_paste_buffer = get_paste_buffer
-else:
-    # Running on Linux
-    try:
-        with open(os.devnull, 'w') as DEVNULL:
-            subprocess.check_call(['uptime', '|', 'xclip'], stdin=subprocess.PIPE, stdout=DEVNULL, stderr=DEVNULL)
-        can_clip = True
-    except (subprocess.CalledProcessError, OSError, IOError):
-        pass  # something went wrong with xclip and we cannot use it
-    if can_clip:
-        def get_paste_buffer():
-            """Get the contents of the clipboard for Linux OSes.
-
-            :return: str - contents of the clipboard
-            """
-            xclipproc = subprocess.Popen(['xclip', '-o', '-selection', 'clipboard'], stdin=subprocess.PIPE,
-                                         stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-            stdout, stderr = xclipproc.communicate()
-            if six.PY3:
-                return stdout.decode()
-            else:
-                return stdout
+        import unicodedata
+        pb_str = unicodedata.normalize('NFKD', pb_unicode).encode('ascii', 'ignore')
 
-        def write_to_paste_buffer(txt):
-            """Paste text to the clipboard for Linux OSes.
+    return pb_str
 
-            :param txt: str - text to paste to the clipboard
-            """
-            xclipproc = subprocess.Popen(['xclip', '-selection', 'clipboard'], stdin=subprocess.PIPE,
-                                         stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-            if six.PY3:
-                xclipproc.stdin.write(txt.encode())
-            else:
-                xclipproc.stdin.write(txt)
-            xclipproc.stdin.close()
-
-            # but we want it in both the "primary" and "mouse" clipboards
-            xclipproc = subprocess.Popen(['xclip'], stdin=subprocess.PIPE, stdout=subprocess.PIPE,
-                                         stderr=subprocess.PIPE)
-            if six.PY3:
-                xclipproc.stdin.write(txt.encode())
-            else:
-                xclipproc.stdin.write(txt)
-            xclipproc.stdin.close()
-    else:
-        # noinspection PyUnusedLocal
-        def get_paste_buffer(*args):
-            """For Linux without the appropriate tool installed to get text from clipboard, raise an exception."""
-            raise OSError(pastebufferr % ('xclip', 'On Debian/Ubuntu, install with "sudo apt-get install xclip"'))
 
-        write_to_paste_buffer = get_paste_buffer
+def write_to_paste_buffer(txt):
+    """Copy text to the clipboard / paste buffer.
+
+    :param txt: str - text to copy to the clipboard
+    """
+    pyperclip.copy(txt)
 
 
 class ParsedString(str):
diff --git a/docs/install.rst b/docs/install.rst
index 78b330fc..6d293176 100644
--- a/docs/install.rst
+++ b/docs/install.rst
@@ -105,6 +105,7 @@ the following Python packages are installed:
 
   * six
   * pyparsing
+  * pyperclip
 
 
 Upgrading cmd2
diff --git a/setup.py b/setup.py
index 3b3b58b5..c29c20f7 100755
--- a/setup.py
+++ b/setup.py
@@ -56,10 +56,10 @@ Programming Language :: Python :: Implementation :: PyPy
 Topic :: Software Development :: Libraries :: Python Modules
 """.splitlines())))
 
-INSTALL_REQUIRES = ['pyparsing >= 2.0.1', 'six']
+INSTALL_REQUIRES = ['pyparsing >= 2.0.1', 'pyperclip', 'six']
 # unitest.mock was added in Python 3.3.  mock is a backport of unittest.mock to all versions of Python
 TESTS_REQUIRE = ['mock', 'pytest']
-DOCS_REQUIRE = ['sphinx', 'sphinx_rtd_theme', 'pyparsing', 'six']
+DOCS_REQUIRE = ['sphinx', 'sphinx_rtd_theme', 'pyparsing', 'pyperclip', 'six']
 
 setup(
     name="cmd2",
diff --git a/tox.ini b/tox.ini
index 869a53ce..6dd6f08e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -7,6 +7,7 @@ deps =
   codecov
   mock
   pyparsing
+  pyperclip
   pytest
   pytest-cov
   six