Description of problem:

When creating a detailed HTML report gcovr prints the following traceback:

```
Traceback (most recent call last):
  File "/usr/bin/gcovr", line 2323, in <module>
    print_html_report(covdata, options.html_details)
  File "/usr/bin/gcovr", line 1593, in print_html_report
    commondir = commonpath(files)
  File "/usr/bin/gcovr", line 413, in commonpath
    for a, b in itertools.izip( dirs, common_dirs ):
```

The `itertools.izip` function was removed in python 3 and should be replaced with a call to the global `zip` function [1].  The bug [2] and a possible patch [3] were already reported/suggested to upsteam, but are not yet integrated into the upstream master.


Version-Release number of selected component (if applicable):

Name        : gcovr
Arch        : noarch
Epoch       : 0
Version     : 3.3
Release     : 2.fc25


How reproducible:

I tried to set up a minimal reproducible project but the bug only seems to occur within a more complex build setup.  The command line to trigger the issue looks like:

gcovr \
   --gcov-executable ${GCOV_EXECUTABLE} \
   --object-directory ${CMAKE_BINARY_DIR} \
   --root ${CMAKE_SOURCE_DIR} \
   --delete \
   --html \
   --html-details \
   --output ${CMAKE_PROJECT_NAME}.cov.html \

Other invocations with a simple text output or a summary html file work as expected.

Steps to Reproduce:
- see above

Actual results:
Program terminates with traceback, creating no detailed HTML report.


Expected results:
Program creates detailed HTML report and exits.

Additional info:

[1]: http://www.diveintopython3.net/porting-code-to-python-3-with-2to3.html#itertools
[2]: https://github.com/gcovr/gcovr/pull/163
[3]: https://patch-diff.githubusercontent.com/raw/gcovr/gcovr/pull/163.patch