For general questions:

The latest 6.0 release appears to have an issue (had this on linux ubuntu/16.04) with the unicode version python was compiled with. I believe the wheels were built assuming a python with ucs2 unicode support, while the actual target python is ucs4 unicode.

We hit an ImportError:

ImportError: /foo/bar/venv/local/lib/python2.7/site-packages/cx_Oracle.so: undefined symbol: PyUnicodeUCS2_Decode

Target python is ucs4:

$ python -c "import sys; opts = {1114111: 'ucs4', 65535: 'ucs2'}; print(opts.get(sys.maxunicode));"
ucs4

1. What is your version of Python? Is it 32-bit or 64-bit?
   64-bit

2. What is your version of cx_Oracle?
   6.0

3. What is your version of the Oracle client (e.g. Instant Client)? How was it
   installed? Where is it installed?
   instantclient version installed: 12.1.0. Installed via npm @ /opt/oracle/instantclient.

4. What is your version of the Oracle Database?
   irrelevant.

5. What is your OS and version?
   Ubuntu 16.04

6. What compiler version did you use? For example, with GCC, run
   gcc --version.
   gcc (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609 (irrelevant)

7. What environment variables did you set? How exactly did you set them?
   ORACLE_HOME, set ld cache via sudo ldconfig and the corresponding file in /etc/ld.so.conf.d

8. What exact command caused the problem (e.g. what command did you try to
   install with)? Who were you logged in as?

python -c "import cx_Oracle;"

9. What error(s) you are seeing?

ImportError: /foo/bar/venv/local/lib/python2.7/site-packages/cx_Oracle.so: undefined symbol: PyUnicodeUCS2_Decode