Repository: pandas-dev/pandas

Issue:
ImportError with pandas 0.20.0 and 0.20.1
#### Code Sample, a copy-pastable example if possible

With versions 0.20.0 and 0.20.1, I get the following error:
```python
import pandas
```
```
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/smiel/.venvs/foo/local/lib/python2.7/site-packages/pandas/__init__.py", line 58, in <module>
    from pandas.io.api import *
  File "/home/smiel/.venvs/foo/local/lib/python2.7/site-packages/pandas/io/api.py", line 8, in <module>
    from pandas.io.clipboard.clipboard import read_clipboard
  File "/home/smiel/.venvs/foo/local/lib/python2.7/site-packages/pandas/io/clipboard/__init__.py", line 103, in <module>
    copy, paste = determine_clipboard()
  File "/home/smiel/.venvs/foo/local/lib/python2.7/site-packages/pandas/io/clipboard/__init__.py", line 76, in determine_clipboard
    return init_qt_clipboard()
  File "/home/smiel/.venvs/foo/local/lib/python2.7/site-packages/pandas/io/clipboard/clipboards.py", line 49, in init_qt_clipboard
    from PyQt4.QtGui import QApplication
ImportError: No module named sip
```
This does not occur with 0.19.2

Here are the other packages installed in my virtualenv
```
$ pip freeze
appdirs==1.4.3
numpy==1.12.1
packaging==16.8
pandas==0.20.1
pyparsing==2.2.0
python-dateutil==2.6.0
pytz==2017.2
PyYAML==3.12
six==1.10.0
```

#### Problem description

It would be nice if pandas was pip installable. As it stands, the new versions are not (for me).

#### Expected Output

No error when importing pandas.

#### Output of ``pd.show_versions()``

I can't get that info without being able to import pandas.




Discussion:
@jorisvandenbossche did you see something like this earlier?
Not exactly this error, but possibly related. For me the error with clipboard was something with ``from PyQt4 import QtCore``. 
For some reason, I had an empty PyQt4 package in site-packages next to PyQt5 (so `import PyQt4` did work, which is used to check which clipboard backend to use, but then later on actual imports raise an error), and for some reason this started to give problems. Matplotlib also had this problem, so I am not sure it was pandas-related. 
@FragLegs Is this in a clean (newly made) env? Or if not, can you see if you can reproduce it then as well?

Resolving patch:
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -1382,8 +1382,8 @@ def to_clipboard(self, excel=None, sep=None, **kwargs):
           - Windows: none
           - OS X: none
         """
-        from pandas.io.clipboard import clipboard
-        clipboard.to_clipboard(self, excel=excel, sep=sep, **kwargs)
+        from pandas.io import clipboards
+        clipboards.to_clipboard(self, excel=excel, sep=sep, **kwargs)
 
     def to_xarray(self):
         """
diff --git a/pandas/io/api.py b/pandas/io/api.py
--- a/pandas/io/api.py
+++ b/pandas/io/api.py
@@ -5,7 +5,7 @@
 # flake8: noqa
 
 from pandas.io.parsers import read_csv, read_table, read_fwf
-from pandas.io.clipboard.clipboard import read_clipboard
+from pandas.io.clipboards import read_clipboard
 from pandas.io.excel import ExcelFile, ExcelWriter, read_excel
 from pandas.io.pytables import HDFStore, get_store, read_hdf
 from pandas.io.json import read_json
diff --git a/pandas/io/clipboard/clipboard.py b/pandas/io/clipboards.py
similarity index 100%
rename from pandas/io/clipboard/clipboard.py
rename to pandas/io/clipboards.py


Test patch: