Readd flake8 build requirement

Fix build because pangox has been retired for F33 so we need remove the BR
  gtkglext
Also remove all gtk stuff (we have to choose between gtk or qt when build opencv)
  https://answers.opencv.org/question/215066/gtk-or-qt-when-build-opencv/
Doxygen requires gtk2, disabling for now

opencv.spec

@@ -90,7 +90,6 @@ BuildRequires:  pkgconfig(nppc-%{?_cuda_rpm_version})
 }
 %{?with_eigen2:BuildRequires:  eigen2-devel}
 %{?with_eigen3:BuildRequires:  eigen3-devel}
-BuildRequires:  gtk3-devel
 BuildRequires:  libtheora-devel
 BuildRequires:  libvorbis-devel
 %if 0%{?fedora} || 0%{?rhel} > 7
@@ -105,7 +104,6 @@ BuildRequires:  libpng-devel
 BuildRequires:  libtiff-devel
 BuildRequires:  libGL-devel
 BuildRequires:  libv4l-devel
-BuildRequires:  gtkglext-devel
 BuildRequires:  OpenEXR-devel
 %{?with_openni:
 BuildRequires:  openni-devel
@@ -119,6 +117,7 @@ BuildRequires:  pkgconfig
 BuildRequires:  python3-devel
 BuildRequires:  python3-numpy
 BuildRequires:  pylint
+BuildRequires:  python3-flake8
 BuildRequires:  swig >= 1.3.24
 %{?with_ffmpeg:BuildRequires:  ffmpeg-devel >= 0.4.9}
 %if 0%{?fedora} || 0%{?rhel} > 7
@@ -134,10 +133,10 @@ BuildRequires:  tesseract-devel
 BuildRequires:  protobuf-devel
 BuildRequires:  gdal-devel
 BuildRequires:  glog-devel
-BuildRequires:  doxygen
+#BuildRequires:  doxygen
 BuildRequires:  python3-beautifulsoup4
 #for doc/doxygen/bib2xhtml.pl
-BuildRequires:  perl-open
+#BuildRequires:  perl-open
 BuildRequires:  gflags-devel
 BuildRequires:  SFML-devel
 BuildRequires:  libucil-devel
@@ -483,7 +482,15 @@ popd
 %{_libdir}/libopencv_xphoto.so.%{abiver}*
 
 %changelog
-* Sun Jun 14 2020 Adrian Reber <adrian@lisas.de> - 4.3.0-4
+* Sun Jun 21 2020 Sérgio Basto <sergio@serjux.com> - 4.3.0-4
+- Readd flake8 build requirement
+- Fix build because pangox has been retired for F33 so we need remove the BR
+  gtkglext
+- Also remove all gtk stuff (we have to choose between gtk or qt when build opencv)
+  https://answers.opencv.org/question/215066/gtk-or-qt-when-build-opencv/
+- Doxygen requires gtk2, disabling for now
+
+* Sun Jun 14 2020 Adrian Reber <adrian@lisas.de>
 - Rebuilt for protobuf 3.12
 
 * Tue Jun 02 2020 Orion Poplawski <orion@nwra.com> - 4.3.0-3