First of all, having "socialist tendencies" isn't exactly a proper interpretation category when it comes to history. How are you gonna measure, or see those tendencies ? Because we have universal healthcare in 2017 means we have socialist tendencies ? Or because we elected a President coming from the Socialist Party in 2012 ? Is the Socialist Party still socialist ?

Also, your question encompasses a lot of moments and rests on the eventuality of a possibility, which is quite hard to answer.

I'd say the first "red scare" that France has known was in 1871, during the Commune de Paris. One might argue that it was not a Communist movement but an Anarchist one, but it's one of the closest we got from departing liberal capitalism altogether. I'd recommend reading on it, it's a fascinating event, often forgotten in French history, and with very interesting characters, like Louise Michel.

For the period that followed the Russian Revolution, you've got to understand that revolutions don't just happen because of tendencies. It helps, but the whole socio-economical context is way more helpful to understand the triggering of a revolt. Russia was in very delayed state of development in 1917, with authoritarian political system based on inheritance. France was a parlementary democracy since 1870 (give or take) and left-wing politicians have been intergrated to government.

You could also explain the absence of revolution by the internal divisions of French socialists. In 1920, the Tours congress of the SFIO (French Section of the Workers International) saw an explosion of what was the great leftist party, between socialists and communists. The secession was based on the adhesion, or not, to the 3rd Internationale. Basically, the socialists refused it and leaned towards a reformist line, the communists joined it and kept their revolutionnary stance. It durably influenced the French left-wing and it was only periodically that communists accepted to rule with socialists (in 1936, 1946 or 1981 for example). Starting from here, the Communist party (SFIC then PCF) became slowly marginalized where it was, at first, the most powerful party. The SFIO (that became the actual Socialist Party) became the leading left-wing party and pushed for reforms aimed at workers that could undermine any revolutionary tendencies. For example, Leon Blum alliance in 1936 passed the first paid vacations for workers, alongside limitations on the workday. In 1946, a socialist-communist coalition voted the Social Security as we know it today. And it was Mitterrand in 1981, the first Socialist president of the 5th Republic, who passed, the fifth week of paid vacation.

A third reason that one might point out is intellectual, and has more to do with later events. After the WW2, marxist was outrageously dominant in the intellectual field of France. It had its critics obviously, but the universities were essentially held by marxists, maoists and trotskysts. During the 70s/80s, there was some sort of an intellectual reaction, especially after the events of May 68 and the publication of Soljenitsyne's book. We saw an actual anti-communist intellectual wave that try to counter the cultural hegemony (hehe) of marxist in social sciences and the humanities. This led to the "New philosophers" movement and a general delegitimization of the whole communist movement. A few political choices also helped, as the PCF was very close to Moscow and refused to denounce some foreign intervention by the USSR.

The failure of Mitterrand governance during the first two years (when he was governing with the PCF) was the final blow to the communist party and the revolutionnary stance of a large part of the French left. In the early 90s, the PCF was polling below 5% and the Socialist party officially embraced globalized capitalism.

I could go more into details for every point that I made but it's 7:43 am and I need a breakfast. Don't hesitate to ask for more details or sources, I have them if you want. But in general, a good line of explanation for "why we haven't had a socialist regime" is a mixture of social, political, economical and cultural context. I also probably forgot tons of stuff, this answer is a mere introduction to the problem, not the exhaustion of every lead.