Sigmon 180 notebooks exec failing

Context

• https://its.cern.ch/jira/browse/SIGMON-180

What was done

• Changed check_dataframe_empty: now it uses inspect.signature instead of inspect.getfullargspecs. For some reason the latter was not working properly and it's also deprecated according to the python documentation.
• Fixed analyze_i_earth_pcnt_pc

QA

• template link to sonar issues: http://sonar.cern.ch/project/issues?branch=SIGMON-180_notebooks_exec_failing&id=lhc-sm-api&resolved=false

Review objectives

• ? assessment of code functionality
• ? assessment of code quality